View source for InterCity 125

{{Short description|British high-speed diesel passenger train}}
{{Use dmy dates|date=April 2024}}
{{Redirect|High Speed Train|high-speed trains in general|High-speed rail}}
{{more citations needed|date=October 2017}}<!--many paragraphs without references, especially in Introduction, Regions, and Numbering sections-->
{{Infobox locomotive
| name = InterCity 125 or High Speed Train (HST)
| powertype = Diesel-electric
| image = British Rail Class 43 at Chesterfield.jpg
| caption = An InterCity 125 in original British Rail livery
| builddate = 1975–1982
| uicclass = Bo'Bo' + 2'2' + ... + 2'2' + Bo'Bo'
| gauge = 
| length = 
| locoweight = 
| electricsystem = 
| maxspeed = {{convert|125|mph|abbr=on|round=5}}
| poweroutput = ''Engine:'' 2x {{convert|2250|bhp|0|abbr=on|lk=in}}
| tractiveeffort = ''Maximum:'' 2x {{convert|17980|lbf|kN|sigfig=3|abbr=on|lk=on}}<br />''Continuous:'' 2x {{convert|10340|lbf|kN|sigfig=3|abbr=on}} @{{convert|64.5|mph|km/h|sigfig=3|abbr=on}}
| disposition = in service
| operator = {{collapsible list|title=''Current:''
|[[ScotRail]] (since 2018)
|[[Interoceanic Corridor of the Isthmus of Tehuantepec]] (since 2023)<ref>{{Cite web|url=https://www.railjournal.com/fleet/mexico-receives-british-hst-fleet-for-isthmus-of-tehuantepec-railway/|title=Mexico receives British HST fleet for Isthmus of Tehuantepec railway |work=International Railway Journal |date=20 September 2023 |url-access=limited}}</ref>
|[[Network Rail]] (since 2003)
|[[Great Western Railway (train operating company)|Great Western Railway]] (since 1998)
|[[Colas Rail]] (since 2007)
|Data Acquisition & Testing Services (DATS)
|Romic Group (Since 2025)<ref>{{cite web | title=Romic Group launch HST as part of expansion into charter market | url=https://www.railadvent.co.uk/2025/10/romic-group-launch-hst-as-part-of-expansion-into-charter-market.html }}</ref>
}}

{{collapsible list|title=''Former:''
|[[British Rail]] (1976–1997)
|[[Great Western Trains]] (1996–1998)
|[[Virgin Trains West Coast]] (1997–2004)
|[[Virgin CrossCountry]] (1997–2003, 2005)
|[[CrossCountry]] (2007-2023)
|[[Midland Mainline (train operating company)|Midland Mainline]] (1996–2007)
|[[Cotswold Rail]] (2000–2010)
|[[GNER]] (1996–2007)
|[[National Express East Coast]] (2007–2009)
|[[East Coast (train operating company) |East Coast]] (2009–2015)
|[[Virgin Trains East Coast]] (2015–2018)
|[[London North Eastern Railway]] (2018–2019)
|[[Grand Central (train operating company)|Grand Central]] (2007–2017)
|[[East Midlands Trains]] (2007–2019)
|[[Hull Trains]] (2019)
|[[East Midlands Railway]] (2019–2021)
|[[Abellio ScotRail]] (2018–2022)
}}
}}

The '''InterCity 125''' (originally '''Inter-City 125''') or '''High Speed Train''' ('''HST''') is a diesel-powered [[High-speed rail|high-speed]] passenger train built by [[British Rail Engineering Limited]] between 1975 and 1982. A total of 95 sets were produced, each comprising two [[British Rail Class 43 (HST)|Class 43]] [[power car]]s, one at each end, and a  [[rake (train)|rake]] of seven or eight [[British Rail Mark 3|Mark 3]] coaches. The name is derived from its top operational speed of {{convert|125|mi/h|km/h|abbr=on}}. At times, the sets have been classified as '''British Rail Classes 253, 254 and 255'''.

British Rail (BR) initially developed the HST as an interim measure in the early 1970s, as delays and cost concerns began to threaten their primary high-speed train project, the [[Advanced Passenger Train]] (APT). The HSTs are now widely considered to be among the most successful trains to have operated on the British railway network, both in terms of their initial impact and their longevity: their introduction into service between 1976 and 1982 resulted in significantly reduced journey times, and large increases in patronage on the routes on which they were operated. The trains proved to be a reliable workhorse, remaining in front-line service for decades. The first withdrawals began in 2017, 41{{nbsp}}years after they were introduced. {{As of|2023|September}}, InterCity 125s remain in service with [[ScotRail]], [[Great Western Railway (train operating company)|Great Western Railway]], and [[Network Rail]].

The design became the basis for an Australian variant, the [[New South Wales XPT|Express Passenger Train (XPT)]], which entered service in [[New South Wales]] in 1982.

==Background==
In the late 1950s and early 1960s, the [[British Transport Commission]] (BTC) was modernising its rail network. It wanted to increase intercity speeds so that railways could compete more effectively with motorways. The governments of the time were unwilling to fund dedicated high speed rail infrastructure, as happened in other countries, and so the BTC instead focused on developing new trains which could operate at higher speed using existing infrastructure. A team of engineers was assembled at the [[Railway Technical Centre]] in [[Derby]] in the early 1960s, to design and develop an [[Advanced Passenger Train]] (APT) capable of at least {{convert|125|mph|km/h}} incorporating many features not previously seen on British railways—such as [[Tilting train|tilting]] to allow higher speeds on curves.{{sfn|Marsden|2001|pages=7–10}}

The APT project suffered repeated delays and in 1970, the [[British Railways Board]] (BRB) decided it would not be sufficiently developed to enter public service  until well into the next decade, so a stopgap solution would be needed to reduce journey times in order to compete effectively with other modes of transport. At the instigation of [[Terry Miller (engineer)|Terry Miller]], Chief Engineer (Traction & Rolling Stock), the BRB authorised the development of a high-speed diesel train using tried and tested conventional technology for short-term use, until the APT was able to take over. An operational prototype was to be built by 1972.{{sfn|Marsden|2001|pages=10–11}}

==Development==
===Concept and design===
The high-speed diesel train, which became the HST or InterCity 125, was formed of a [[rake (train)|rake]] of [[British Rail Mark 3|Mark 3]] passenger coaches between two [[streamliner|streamlined]] power cars, one at each end. Each power car was fitted with a [[Paxman Valenta]] diesel engine which could produce {{convert|2250|hp|lk=on}}. This engine was chosen due to its light weight, and subsequent high [[power-to-weight ratio]]. The decision to use two power cars was taken early in the project as design engineers calculated that the train would need {{convert|4500|hp}} to sustain 125{{nbsp}}mph on the routes for which it was designed (the [[Great Western Main Line]], [[East Coast Main Line]], [[Midland Main Line]], and the [[Cross Country Route]]), and it was established that no "off-the-shelf" diesel engine was capable of producing such power.<ref name="Semmens1990">{{cite book |last1=Semmens |first1=Peter |title=Speed On The East Coast Main Line: A Century and a Half of Accelerated Services|date=1990 |publisher=Patrick Stephens Ltd |isbn=0-85059-930-X |pages=129–225}}</ref><ref name="CC125">{{cite web |title=Trackside Classic: 1976 British Rail Inter City 125 High Speed Train – Still Setting The Standard |date=18 October 2021 |url=https://www.curbsideclassic.com/trackside-classic/trackside-classic-1976-british-rail-inter-city-125-high-speed-train-still-setting-the-standard/ |publisher=Curbside Classic |access-date=30 March 2022}}</ref> 
[[File:The_Birmingham_Pullman_passing_High_Wycombe,_geograph_4105938_by_john_bristow_(crop).jpg|thumb|The [[Blue Pullmans]], which were in service between 1960 and 1973, are often seen as forerunners of the HSTs.]]
British Rail had used a similar idea of a train with integral power cars at each end a decade earlier, with their [[Blue Pullman]] sets; although these trains were not ultimately commercially successful, they established the validity of the idea, and are often seen as forerunners of the HSTs.<ref name="CCBP">{{cite web |title=Trackside Classic: 1960 British Railways Metro Cammell 'Blue Pullman' – Another Forgotten Pioneer |date=3 May 2020 |url=https://www.curbsideclassic.com/trackside-classic/trackside-classic-1960-british-railways-metro-cammell-blue-pullman-another-forgotten-pioneer/ |publisher=Curbside Classic |access-date=13 April 2022}}</ref> The concept had several advantages; firstly, a power car at each end allowed the train to be driven from either end in [[Push–pull train|push–pull formation]] with the power cars linked by electronic control systems, and therefore reverse direction without the need for a locomotive to be run around at terminus stations, secondly, the train could run with only one power car operational, though at reduced speed, therefore allowing a journey to continue in the event of a breakdown, and thirdly, it avoided the underfloor diesel engines found in [[diesel multiple unit]]s, therefore avoiding noise and vibration for passengers.<ref name="CC125"/> Another factor was that two locomotives operating in push–pull formation, would cause less wear on the rails than a single locomotive. One of the design requirements for the HST was that it should exert no more force on the track at 125{{nbsp}}mph, than a [[British Rail Class 55|Class 55 'Deltic']] locomotive at 100{{nbsp}}mph, and each power car of the HST weighed a modest 70{{nbsp}}tons which allowed it to meet this requirement.<ref name="Semmens1990"/>

One of the key design requirements for the HSTs was that they should be able to run at 125{{nbsp}}mph on existing infrastructure. In order to achieve this, they had to be able to come to a stop from 125{{nbsp}}mph within existing [[railway signal|signal]] spacings, which required a high performance [[Railway brake|braking]] system to be developed. This was achieved by a high performance [[disc brake]] system, in place of the [[clasp brake]]s used on traditional stock.<ref name="Semmens1990"/><ref name="CC125"/>

===Prototype===
{{main|British Rail Class 252}}
{{see also|British Rail Class 41 (HST){{!}}British Rail Class 41}}
[[File:252001 - weston s mare - 1975.jpg|thumb|[[British Rail Class 252|Class 252]] prototype HST at [[Weston-super-Mare railway station|Weston-super-Mare]] in 1975]]
To prove the concept, British Rail produced a [[prototype]]. The framework of the new locomotive, classified [[British Rail Class 41 (HST)|British Rail Class 41]], was built at [[Crewe Works]] and transferred to [[Derby Litchurch Lane Works]] for completion. The design incorporated a driving desk around the centrally seated driver, a sound-proofed door between the cab and the engine room, and, unusually, no side windows.{{sfn|Marsden|2001|pages=15–16}} The prototype was the first diesel locomotive in British railway history to use [[alternating current|AC]] alternators in place of a [[direct current|DC]] generator, with the output converted to DC when used for traction.{{sfn|Marsden|2001|page=16}}

The prototype train of seven coaches and two locomotives was completed in August 1972 and in the autumn was running trials on the main line. The following year, high-speed testing was undertaken on the "racing stretch" of the [[East Coast Main Line]] between [[York railway station|York]] and [[Darlington railway station|Darlington]]. The set was reduced to two power cars and five trailers, and there was a concerted attempt to see how fast the train would go. On 6 June 1973, {{convert|131|mph|km/h|abbr=on}} was reached, which was bettered as the days passed. On 12 June, a world diesel speed record of {{convert|143.2|mph|km/h|abbr=on}} was achieved, and the drivers believed that 150&nbsp;mph was possible, but the BRB issued instructions for the high speed tests to cease. It was believed at the time that this was because the BRB wanted to promote the APT as the future of high speed rail travel in the UK.<ref>Railway Performance Society "HST 40 Glorious Years" 2016 p8</ref>

The fixed-formation concept was proven in trial running between 1973 and 1976, and British Rail went on to build 95 sets of production HSTs to transform InterCity services.<ref name="Semmens1990"/>

===Production versions===
{{also|British Rail Class 43 (HST)}}
Manufacturing of the production power car sets began in 1974 at the [[Crewe Works]], with the Mark 3 coaches being manufactured at the [[Derby Litchurch Lane Works]]. The first production power car, numbered 43002, was delivered in late 1975. The production versions were mechanically very similar to the prototype, but differed considerably in appearance: the streamlined wedge-shaped front end lacked conventional buffers, and the [[drawgear]] was hidden under a cowling. The single cab front window was much wider than the prototype's, and side windows were included. Unlike the prototype, no driving position was included at the inner end, as the power cars were originally intended to operate in fixed formation.<ref name="Semmens1990"/><ref name="CC125"/>
[[File:Intercity 125 2169045.jpg|thumb|An InterCity 125 about to depart [[Manchester Piccadilly]] in 1986]]
The train's appearance is the work of British industrial designer [[Kenneth Grange]] who was approached by British Rail to design the livery, but under his own impetus, and without telling anyone, decided to redesign the body. He worked with an aerodynamic engineer, and they built and tested a model in a [[wind tunnel]].<ref>{{cite web |title=How we made the InterCity 125 |url=https://www.theguardian.com/culture/2013/sep/09/how-we-made-intercity-125 |work=The Guardian |access-date=1 June 2022 |date=9 September 2013}}</ref> "It really was rather quite brutal, rather clumsy. I thought, 'Oh I'd like to get my hands on that', although the brief was nothing to do with the shape, absolutely not at all."<ref>Channel 5 documentary ''Intercity 125'' episode 1, broadcast 15 May 2018</ref>  He presented the new design to British Rail and persuaded them to adopt it.<ref>{{cite news |url= https://www.ft.com/content/2221b178-87f6-11e0-a6de-00144feabdc0 |title= Everywhere and Nowhere |newspaper= Financial Times |location= London |date=27 May 2011 |access-date=21 August 2011}}</ref> In 2016 [[Great Western Railway|GWR]] renamed 43002 "Sir Kenneth Grange" in his honour, at the same time returning it to its original blue and yellow paint scheme. After being withdrawn from GWR service, 43002 was acquired by the National Collection in November 2019 and was displayed at the [[National Railway Museum]] in York.<ref>{{cite web |title=Class 43 High-Speed Train, also known as the InterCity 125, is unveiled at National Railway Museum in York. |date=11 November 2019 |url=https://www.railwaymuseum.org.uk/about-us/press-office/high-speed-locomotive-sir-kenneth-grange-joins-national-railway-museum |publisher=Railway Museum |access-date=1 June 2022}}</ref>

The redesigned front end also had the advantage of easing [[trade union|union]] acceptance of the train: the railway union [[ASLEF]] had objected to the prototype's lack of space for a [[secondman]] to sit alongside the driver, and had refused to operate the prototype in public service. The cab on the production version was wide enough to accommodate two people, and so was able to overcome these objections.<ref name="Semmens1990"/><ref name="CC125"/> 

An InterCity 125 consists of two [[British Rail Class 43 (HST)|Class 43]] diesel-electric power cars, each powered originally by 2,250 [[Brake horsepower|bhp]] (1,678 [[kW]]) [[Paxman Valenta]] engines (they have [[#Re-engining and refurbishment|since been fitted]] with different engines), and a set of six to nine [[British Rail Mark 3|Mark 3]] coaches.

Key features of the design are the high power-to-weight ratio of the locomotives (1678&nbsp;kW per ~70-tonne loco),<ref>{{cite book| author= Marsden, Colin | publisher = Ian Allan | year= 2001| title= HST: Silver Jubilee | page = foreword |isbn = 0-7110-2847-8}}</ref> which were built for high-speed passenger travel, improved [[crashworthiness]] over previous models, and [[push-pull train|bi-directional running]] avoiding the need for the locomotive to run around at terminating stations.<ref>{{cite web |url=http://www.nrm.org.uk/OurCollection/LocomotivesAndRollingStock/CollectionItem.aspx?objid=1988-7000 |title=HST Power Car |publisher=[[National Railway Museum]] |access-date=18 May 2009 |archive-date=11 October 2013 |archive-url=https://web.archive.org/web/20131011100217/http://www.nrm.org.uk/OurCollection/LocomotivesAndRollingStock/CollectionItem.aspx?objid=1988-7000 |url-status=dead }}</ref> Until the HST's introduction, the speed of British diesel-powered trains was limited to {{convert|100|mph|km/h|0|abbr=on}}.<ref name = 'EarlyHighspeedBR' >{{cite journal
  | title=High speed track on the Western Region of British Railways 
  |last= Collins  |first=R.J. 
  |volume=64  |issue=2
  |date=May 1978
  |pages=207–225
  |journal=Proceedings of the Institution of Civil Engineers
  |url=http://www.icevirtuallibrary.com/doi/abs/10.1680/iicep.1978.2755
  |doi=10.1680/iicep.1978.2755 
  | publisher= [[Institution of Civil Engineers]] 
  | access-date = 2 October 2015
|url-access=subscription}}</ref> The HST allowed a 25% increase in service speeds along many of the lines on which they operated.

Lighter axle loading allowed the trains to travel faster than conventional services along lines not suited to full-speed running, such as [[Edinburgh to Aberdeen line|Edinburgh to Aberdeen]]. Coupled with superior acceleration over older locomotives, this allowed substantial cuts in journey times. The increased speed and rapid acceleration and deceleration of the HST made it ideal for passenger use.

==British Rail service==
===Introduction into service===
Deliveries continued in 1976, and on 4 October a partial service of HSTs running at {{convert|125|mi/h|km/h|abbr=on}} began on the [[Western Region of British Railways|Western Region]], from {{stnlnk|London Paddington}}, on the [[Great Western Main Line|Great Western]] and [[South Wales Main Line]]s.<ref name=bbc1976/> The radical update of the standard BR livery on the power cars was complemented by the 'Inter-City 125' branding, which also appeared on timetables and promotional literature.<ref name=bbc1976>{{cite news |title=New train speeds into service |url=https://news.bbc.co.uk/onthisday/hi/dates/stories/october/4/newsid_2486000/2486817.stm |access-date=15 May 2019 |work=BBC News |publisher=British Broadcasting Corporation |date=4 October 1976}}</ref> By the start of the summer timetable in May 1977, the full complement of 27 Class 253 sets (253001–253027) was in service on the Western Region, replacing locomotive-hauled trains on the Bristol and South Wales routes. Passenger numbers rapidly increased due to the speed and frequency of the services. The displacement by HSTs of [[British Rail Class 50|Class 50]] locomotives to slower services effectively finished off the last [[British Rail Class 52|Class 52]] diesel-hydraulics by early 1977.
[[File:12.04.81 Kings Cross Class 254 HSTs (5932012764).jpg|thumb|left|The cab fronts of three HSTs at {{stnlnk|London King's Cross}} in 1981]]
The production of Class 254 continued through 1977 for [[East Coast Main Line]] (ECML) services. The HSTs allocated to the ECML had eight coaches instead of seven on the Western Region, and British Rail had originally planned to fit uprated {{convert|2500|bhp|abbr=on}} Valenta engines to the longer HSTs, but this was not carried out, as it was found that the engine's coolant system would struggle to deal with the extra heat produced by a higher powered engine. The first 125{{nbsp}}mph East Coast HST services were introduced for the summer timetable in May 1978, with HSTs taking over ''[[Flying Scotsman (train)|Flying Scotsman]]'' and other services. The previous generation of [[British Rail Class 55|Class 55 'Deltic']] locomotives were relegated to secondary duties, before being withdrawn entirely in late 1981. A full HST timetable for the ECML was due to be introduced in May 1979, but was delayed until late August due to the [[Penmanshiel Tunnel|Penmanshiel Tunnel collapse]]. The HSTs reduced the [[London King's Cross railway station|London]]-[[Edinburgh Waverley railway station|Edinburgh]] journey time by up to an hour.<ref name="Semmens1990"/>

In 1979, HST services began in [[South West England]], to destinations such as [[Exeter St Davids railway station|Exeter]], {{stnlnk|Plymouth}} and {{stnlnk|Penzance}}, and in 1981 they were introduced to the [[Cross Country Route]] via {{stnlnk|Birmingham New Street}}. In 1982 HSTs were introduced to [[Midland Main Line]] services from [[London St Pancras]]: Although the HSTs were mostly limited to a top speed of {{convert|100|mph}} on those routes, their increased acceleration still reduced journey times.<ref name="Semmens1990"/>   

Ninety-five HST sets, including 197 Class 43 powercars, were built between 1976 and 1982. More Mark 3 trailer cars were built in the 1980s for the Western Region Class 253s, making them eight-car rakes in common with East Coast and Midland Main Line services. During the 1990s only the Cross-Country sets remained as seven-car rakes, with just one first-class coach.

One of the main selling points of the new HST services were the increase in speed and comfort without any increase in fares.<ref name=bbc1976/> The HST brought considerable improvements in service, and British Rail began active marketing to support the train's introduction.<ref>{{Cite news| author1= Owen, A.D. |author2 = Phillips, G.D.A. |publisher= [[University of Bath]] |title= The Characteristics of Railway passenger demand |page=234 |url= http://www.bath.ac.uk/e-journals/jtep/pdf/Volume_XX1_No_3_231-253.pdf}}</ref> The InterCity service was a great success for British Rail.<ref>{{cite web| url=http://www.railwaysarchive.co.uk/documents/DoT_WP001.pdf |title=New opportunities for the railways: the privatisation of British Rail |publisher=Railway Archive | page=8 |access-date=18 May 2009}}</ref>
====Journey time reductions====
One of the main selling points of the HSTs were the reductions they could achieve in journey times, with the trains being marketed in publicity material as 'The Journey Shrinker'. In 1973 British Rail produced a promotional booklet entitled ''Speed for the Seventies'' in which they laid out the expected journey times to be achieved with HSTs compared to the then extant timings.<ref name="Semmens1990"/>
[[File:HST Leamington 1992 (47778069361).jpg|thumb|An HST set in the later [[InterCity (British Rail)|InterCity]] livery at {{rws|Leamington Spa}} in 1992]]
{| class=wikitable style=text-align:center
!colspan=4|Journey times from London 1973 !!colspan=3|Proposed HST times
|-
! Place !! Distance<br> (miles & km) !! Time<br>h.m !! [[Speed#Average_speed|Average Speed]] !! Time<br>h.m !! Average Speed !! Time savings 
|-
| [[Bath Spa railway station|Bath]] || {{convert|107|mi|abbr=on}} || 1.38 || {{convert|66|mph|abbr=on}} || 1.11|| {{convert|90|mph|abbr=on}}|| 27m
|-
| [[Bristol Temple Meads railway station|Bristol]] || {{convert|118|mi|abbr=on}} || 1.50 || {{convert|65|mph|abbr=on}} || 1.22 || {{convert|87|mph|abbr=on}}|| 28m
|-
| [[Cardiff Central railway station|Cardiff]] || {{convert|145|mi|abbr=on}} || 2.11 || {{convert|67|mph|abbr=on}} ||  1.46 || {{convert|82|mph|abbr=on}}|| 25m
|-
| {{stnlnk|Doncaster}} || {{convert|156|mi|abbr=on}} || 2.04 || {{convert|75|mph|abbr=on}} || 1.39 || {{convert|95|mph|abbr=on}}|| 25m
|-
| {{stnlnk|York}} || {{convert|188|mi|abbr=on}} || 2.22 || {{convert|79|mph|abbr=on}} || 2.00 || {{convert|94|mph|abbr=on}}|| 22m
|-
| {{stnlnk|Leeds}} || {{convert|186|mi|abbr=on}} || 2.28 || {{convert|75|mph|abbr=on}} ||  2.14 || {{convert|83|mph|abbr=on}} || 14m
|-
| {{stnlnk|Darlington}} || {{convert|232|mi|abbr=on}} || 2.52 || {{convert|81|mph|abbr=on}} || 2.31 || {{convert|92|mph|abbr=on}} || 21m
|-
| {{stnlnk|Newcastle}} || {{convert|268|mi|abbr=on}} || 3.38 || {{convert|74|mph|abbr=on}} || 2.57 || {{convert|91|mph|abbr=on}} || 41m
|-
| [[Edinburgh Waverley railway station|Edinburgh]] || {{convert|393|mi|abbr=on}} || 5.30 || {{convert|71|mph|abbr=on}} || 4.30 || {{convert|87|mph|abbr=on}} || 60m
|}
Most of these predictions of the journey times achievable by HSTs proved to be quite accurate, and in some cases they were underestimates. For example, the best timing achieved for London to Bath was 62 minutes, and 115 minutes was achieved for London to York.<ref name="Semmens1990"/>
===Proposed electric version===
In the early 1980s, when [[East_Coast_Main_Line#Electrification|electrification of the East Coast Main Line]] was in its early planning stages, serious consideration was given to producing an electric version of the HST, which would have been known as the HST-E. This would have kept the bodyshell and most of the mechanical components of the diesel version, but the power cars would have been [[electric locomotive]]s fitted with [[Pantograph (transport)|pantograph]]s. The thinking was, that as the diesel version had been proven, it would be a straightforward way to produce a 125mph trainset. The HST-E was proposed in response to the failure of the [[Advanced Passenger Train]] (APT) project. This proposal did not proceed, and BR instead developed a new electric trainset which would become the {{convert|140|mph|abbr=on}} capable [[InterCity 225]] to work the electrified services on the ECML, which came into service in the late-1980s.<ref>{{cite web |title=FROM THE ARCHIVES: Class 91s...promise unfulfilled |url=https://www.railmagazine.com/news/rail-features/class-91spromise-unfulfilled |publisher=Rail Magazine |access-date=14 May 2022}}</ref><ref>{{cite book |last1=Semmens |first1=Peter |title=Speed On The East Coast Main Line: A Century and a Half of Accelerated Services|date=1990 |publisher=Patrick Stephens Ltd |isbn=0-85059-930-X |page=235}}</ref>

===World records===
[[File:19880827-KingsCross-HST-43079.jpg|thumb|InterCity 125 at King's Cross in 1988]]
The prototype InterCity 125 (power cars 43000 and 43001) set the [[Land speed record for railed vehicles|world speed record]] for diesel traction at {{convert|143.2|mph|abbr=on}} on 12 June 1973.<ref name="proto">{{cite web|url=http://www.traintesting.com/HST_prototype.htm |title=Testing the prototype HST in 1973 |publisher=traintesting.com |access-date=29 April 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090915204316/http://www.traintesting.com/HST_prototype.htm |archive-date=15 September 2009 }}</ref>

A second [[world record]] for the [[Land speed record for railed vehicles#Diesel|fastest diesel-powered train]], a speed of {{convert|148|mph|abbr=on}}, was set by an HST on 1 November 1987,<ref name='paxhis'/><ref>{{cite news|title=Intelligence August 2002 |date=1 August 2002 |url=http://www.railwaygazette.com/news_view/article/2002/08/4820/intelligence-52.html |work=[[Railway Gazette International]] |location=London |access-date=3 March 2012 |url-status=dead |archive-url=https://web.archive.org/web/20080305050403/http://www.railwaygazette.com/news_view/article/2002/08/4820/intelligence-52.html |archive-date=5 March 2008 }}</ref><ref name='hst1'>{{cite news |title=Rail Timeline |url= https://news.bbc.co.uk/1/shared/spl/hi/programmes/the_day_britain_stopped/timelines/rail/html/1970s.stm |work =BBC News |access-date= 7 April 2008 |location=London}}</ref><ref name='hst2'>{{cite news | first=Russell | last=Hollowood | title=The little train that could |date=16 March 2006 |work=BBC News |url= https://news.bbc.co.uk/2/hi/uk_news/magazine/4812304.stm |access-date = 7 April 2008 |location= London}}</ref> between Darlington and York with a test run for a new type of [[bogie]] for use on [[British Rail Mark 4|Mark 4]] coaches on the same route. The record run was powered by 43102 (at the front) and 43159 (at the rear).<ref name="HST: a preservation">{{cite web |title=HST: a preservation for the nation |url=https://www.railmagazine.com/news/rail-features/hst-a-preservation-for-the-nation |publisher=Rail Magazine |access-date=15 April 2022 |date=16 January 2017}}</ref>

An HST also holds the world speed record for a diesel train carrying passengers.  On 27 September 1985, a special press run for the launch of a new ''[[Tees-Tyne Pullman]]'' service from {{Stnlnk|Newcastle}} to {{Stnlnk|London King's Cross}}, formed of a shortened 2+5 set, briefly touched {{convert|144|mi/h|km/h|abbr=on}} north of {{Stnlnk|York}}. 

==Regions and operators==

===South West England and South Wales===
On the Western Region, InterCity 125 trains (designated class 253) were introduced on services from London to Bristol and South Wales,<ref name="paxhis">{{cite web|title=Paxman and Diesel Rail Traction |publisher=Richard Carr's Paxman history pages |url=http://www.paxmanhistory.org.uk/paxrailt.htm |date=3 March 2012 |access-date=4 March 2012 |url-status=dead |archive-url=https://web.archive.org/web/20110527132704/http://www.paxmanhistory.org.uk/paxrailt.htm |archive-date=27 May 2011 }}</ref> and extended to most daytime services from London to Devon and Cornwall. Some South Wales services were extended to {{rws|Milford Haven}}, {{rws|Fishguard}} and {{rws|Pembroke}} in West Wales. Maintenance was provided at [[Old Oak Common TMD|Old Oak Common]] and [[St Philip's Marsh T&RSMD|St Philip's Marsh]], and [[Laira TMD|Laira]] also carried out maintenance after services to Devon and Cornwall were introduced in 1979.

[[British Rail Class 47]] locomotives still operated cross-country services from Cornwall and South Wales to the North-East via the [[Cross Country Route]], and London to the Midlands/Welsh Marches. Class 43s replaced them when the third batch of power cars was delivered in 2+7 formation with two first class coaches, a buffet car, and four second class coaches between two power cars. They were later expanded to a 2+8 formation, with an extra second class coach.
[[File:43094 at Old Oak Common 2.jpg|thumb|[[First Great Western]] HST passing [[Old Oak Common TMD|Old Oak Common Train Maintenance Depot]] in 2007]]
[[Great Western Trains]] was formed out of the privatisation of British Rail and operated the InterCity routes from London Paddington to the west of England. In 1998 [[FirstGroup]] acquired Great Western Trains and rebranded it [[First Great Western]]. InterCity 125s continued to work the same diagrams they had under British Rail, albeit in a different livery.

[[File:W43002 Sir Kenneth Grange at Bristol Temple Meads.jpg|thumb|43002 received vinyls of its original livery to celebrate the 40th anniversary of the IC125, and was named after the class's designer, Sir Kenneth Grange]]

Great Western Railway used 43 HST sets to operate most intercity services from Paddington to [[Bristol Temple Meads railway station|Bristol]], {{rws|Bath Spa}}, {{rws|Chippenham}}, {{rws|Swindon}}, [[Cardiff Central railway station|Cardiff]], {{rws|Swansea}}, {{rws|Carmarthen}}, {{rws|Cheltenham Spa}}, {{rws|Oxford}}, [[Worcester Shrub Hill railway station|Worcester]], {{rws|Hereford}}, {{rws|Paignton}}, {{rws|Plymouth}} and {{rws|Penzance}}, and some commuter services to {{rws|Westbury}}, {{rws|Taunton}} and {{rws|Exeter St Davids}}. In 2012 all First Great Western's intercity services were worked by InterCity 125 sets with the exception of sleeper services and some Cotswold Line services.

From 2005 the First Great Western HSTs were re-engined with MTU power units and the coaches were refurbished.<ref>{{cite news |url=http://www.accessmylibrary.com/coms2/summary_0286-29301111_ITM |title=Trains undergo GBP63m redesign | publisher = Europe Intelligence Wire |date=18 January 2007 |access-date=18 May 2009}}</ref> Units for services in the M4 corridor/Thames Valley to Bristol, Hereford, Oxford, Exeter and Cardiff were converted to a high-density layout of mostly airline-style seats in standard class (only two tables per coach) to provide more seats for commuters. The remainder, for routes to Swansea and the West Country, included four tables per standard class coach.

The refurbished coaches had new seating (leather in first class), at-seat power points and a redesigned buffet bar.<ref>{{cite web|url=http://www.firstgreatwestern.co.uk/NewsItem.aspx?id=414 |title=New look trains for First Great Western |publisher=[[First Great Western]] |access-date=20 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090213055648/http://www.firstgreatwestern.co.uk/NewsItem.aspx?id=414 |archive-date=13 February 2009 }}</ref> From 2010, one standard class coach in each set had a Volo TV system,<ref>{{Cite news|url=https://www.mirror.co.uk/news/uk-news/trains-screens-show-tv-films-214741|title=Trains get screens to show TV and films|last=Mirror.co.uk|date=14 April 2010|work=mirror|access-date=28 May 2018}}</ref> but this was removed in 2014.

Another change was made in 2014, when some first class coaches were converted to standard class or composite (half standard and half first class), leaving {{frac|1|1|2}} first class coaches per set.<ref>{{Cite news|url=https://www.bbc.co.uk/news/uk-england-bristol-26575102|title=More standard train seating pledge|date=14 March 2014|work=BBC News|access-date=28 May 2018|language=en-GB}}</ref> The first class coaches were refurbished in a more luxurious style, and many tables with one seat each side in first class were replaced by individual airline-style seats.<ref>{{Cite web|url=https://www.businesstraveller.com/news/2014/08/22/first-great-western-unveils-refurbished-first-class-carriages/|archive-url=https://web.archive.org/web/20180528113859/https://www.businesstraveller.com/news/2014/08/22/first-great-western-unveils-refurbished-first-class-carriages/|url-status=dead|archive-date=28 May 2018|title=First Great Western unveils refurbished first class carriages – Business Traveller|date=28 May 2018|access-date=28 May 2018}}</ref>

By mid-2019, Great Western Railway no longer had any HSTs operating service to or from Paddington, having replaced all of them with [[British Rail Class 800|Class 800]] and [[British Rail Class 802|Class 802]].

Great Western Railway retained 24 powercars and 48 coaches to form 11 four-coach sets for use on local services between [[Cardiff Central railway station|Cardiff]] and [[Penzance railway station|Penzance]], replacing the [[British Rail Class 158]].{{when|date=January 2024}} However, by the end of 2022 these sets were proving expensive to operate and increasingly difficult to maintain due to their age. With spare Class 802 sets post-Covid being able to fill in on the route, in December 2022 GWR announced plans to withdraw all of the HST Castle sets from use by December 2023.<ref>{{cite web|url=https://www.modernrailways.com/article/gwr-castle-hsts-go-december-2023|title=GWR HSTs to go in December|publisher=Modern Railways|date=December 2022|accessdate=13 June 2024}}</ref> Whilst leased vehicles were returned to [[Angel Trains]], four directly owned 2+4 Castle sets have been retained by GWR, with plans to retain them until at least December 2024.<ref>{{cite web|url=https://www.modernrailways.com/article/gwr-retain-four-HSTs|publisher=Modern Railways|date=28 April 2023|accessdate=13 June 2024 |title=GWR to retain four HSTS |url-access=subscription}}</ref>

===Eastern England and Scotland===
[[File:Haymarket - VTEC 43295 northbound Highland Chieftain.JPG|thumb|right|''[[Highland Chieftain]]'' InterCity 125 arriving at [[Haymarket railway station|Haymarket]] in 2016]]
On the [[East Coast Main Line]], the InterCity 125 designated Class 254 was the staple stock after the retirement of the [[British Rail Class 55|Class 55 Deltic]] locomotives in 1980–1982, until the introduction of [[InterCity 225]] following electrification in 1990. They were concentrated on services from [[London King's Cross]] to [[Newcastle railway station|Newcastle]] and [[Edinburgh Waverley]], and to [[Glasgow Queen Street]], [[Inverness railway station|Inverness]] and [[Aberdeen railway station|Aberdeen]]. In the months following the [[Penmanshiel Tunnel#Tunnel collapse (1979)|Penmanshiel Tunnel collapse]] in 1979, London to Scotland services ran via the [[Newcastle and Carlisle Railway|Tyne Valley line]] from Newcastle to [[Carlisle railway station|Carlisle]] then to Scotland via the [[West Coast Main Line]]. HSTs were also used on some services from London to [[Leeds railway station|Leeds]], [[Bradford Forster Square railway station|Bradford Forster Square]], [[Cleethorpes railway station|Cleethorpes]], [[Hull Paragon Interchange|Hull]] and [[Scarborough railway station|Scarborough]].

The East Coast (ECML) formation was originally 2 + 8, increased to 2 + 9 in 2002 when extra stock became available. The ECML formation was two first-class coaches, one buffet (with 1st Class seating) and five (later six) standard-class coaches between the buffet and power cars. For a few years, formations included a TRUK (trailer restaurant kitchen) and buffet car, a TS (trailer second class) and TF (trailer first class) coaches, many formations were 4 × TS, TRUK, Buffet, 2 × TF. Nine trailer car units followed this formation, with the addition of a TS. 'Pullman' services replace a TS with an additional first-class coach.

[[File:43367 at Kings Cross.jpg|thumb|left|GNER liveried InterCity 125 departing King's Cross in 2007]] 
After privatisation, InterCity 125s were operated by [[Great North Eastern Railway]] (GNER),<ref>{{cite news |url=http://www.accessmylibrary.com/coms2/summary_0286-32026523_ITM |title=GNER wins British franchise |work=International Railway Journal |date=1 April 2005 |access-date=18 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20131230232951/http://www.accessmylibrary.com/coms2/summary_0286-32026523_ITM |archive-date=30 December 2013 }}</ref> alongside electric [[InterCity 225]] units from London to Newcastle and Edinburgh, and beyond the electrified sections (or where [[British Rail Class 91]]s cannot operate due to route availability restrictions) to [[Kingston upon Hull|Hull]], [[Skipton]], [[Harrogate]], [[Inverness]] and [[Aberdeen]].

In January 2007 the first of GNER's 13 refurbished HSTs was unveiled with coaches rebuilt to the same '[[Great North Eastern Railway#Rolling stock|Mallard]]' standard as its [[InterCity 225]] electric sets with similar seating, lighting, carpets and buffet cars.<ref>{{cite news |url= http://www.thepress.co.uk/news/1252717.makeover_for_gner_125_trains |first=Tom |last= Stirling |title=Makeover for GNER 125 trains |newspaper= The Press |location=York |date=12 March 2007 |access-date=18 May 2009}}</ref> The power cars were upgraded with [[MTU Friedrichshafen|MTU engines]]. The first of the HST Mallards was in service by spring 2007.{{Citation needed|date=March 2012}}
[[File:NXEC HST 43300 S Crozier.jpg|thumb|right|[[National Express East Coast]]  liveried InterCity 125 in 2007]]
In 2007 the franchise was taken over by [[National Express East Coast]] (NXEC), which continued the re-engining programme begun by GNER, and completed the refurbishment of the fleet in March 2009.<ref>{{cite press release|url=http://www.nationalexpressgroup.com/nx1/media/news/sub_news/pr2009/2009-03-17/ |title=National Express East Coast launches final refurbished and upgraded HST power cars back into service |publisher=National Express Group |date=13 March 2009 |access-date=18 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20101129082226/http://nationalexpressgroup.com/nx1/media/news/sub_news/pr2009/2009-03-17/ |archive-date=29 November 2010 }}</ref> Two power cars were transferred to First Great Western early in 2009.<ref name="list">[http://www.garyheelas.plus.com/fleetlist.pdf InterCity 125 Group fleet list] {{webarchive|url=https://web.archive.org/web/20060720021325/http://www.garyheelas.plus.com/fleetlist.pdf |date=20 July 2006 }}.</ref> The final Mallard-upgraded Mark 3 coaches entered service with NXEC in October 2009.{{Citation needed|date=March 2012}}

Following an announcement by [[National Express]] that it would not provide further financial support to NXEC, the franchise ceased on 13 November 2009, and the operation of the route returned to public ownership. As a result, the 13 sets were operated by [[East Coast (train operating company)|East Coast]] from late 2009. East Coast introduced an InterCity 125 service to [[Lincoln Central railway station|Lincoln]] in 2011.<ref>{{cite web|url=https://thelincolnite.co.uk/2011/05/lincoln-welcomes-new-direct-london-route/|title=Lincoln welcomes new direct London route|date=23 May 2011|website=The Lincolnite}}</ref> The InterCity 125 was replaced by the electric InterCity 225 on the line to Skipton when the electrical infrastructure was upgraded. Eight East Coast services per day in each direction used the InterCity 125.{{citation needed|date=December 2013}} In 2012, 43072 (now 43272), 43074 (now 43274) were transferred from [[East Midlands Trains]] and received MTU engines. In April 2015, [[Virgin Trains East Coast]] took over operation of the [[InterCity East Coast]] franchise. All trains passed with the InterCity East Coast franchise to [[London North Eastern Railway]] in June 2018.

[[File:43468 at London Kings Cross.jpg|thumb|left|Grand Central InterCity 125 departing London King's Cross in 2011. All Grand Central Class 43 power cars had exposed front buffers due to previous use as surrogate [[Driving Van Trailer]]s (DVTs).]]
In 2006, [[Grand Central (train operating company)|Grand Central]] obtained six Class 43 power cars to operate its London-Sunderland passenger service via the East Coast Main Line. The service was due to begin in December 2006 although upgrade work to enable the coaching stock (which was formerly used for locomotive-hauled services and had a different electric heating/power supply system) to operate with Class 43 power cars was heavily delayed and therefore pushed the starting date back to 18 December 2007.<ref>{{cite news |url= http://business.timesonline.co.uk/tol/business/industry_sectors/transport/article660581.ece |archive-url= https://web.archive.org/web/20110612140341/http://business.timesonline.co.uk/tol/business/industry_sectors/transport/article660581.ece |url-status= dead |archive-date= 12 June 2011 |title= Delay for Grand Central trains |newspaper=The Times |date=5 October 2006 |access-date=18 May 2009 |location=London |first=Angela |last=Jameson}} {{subscription required}}</ref> HSTs 43084 and 43123 were the final operational [[Paxman Valenta]] power cars, being re-engined in 2010 with the same MTU engines as other units. While at the works being re-engined, Grand Central added the orange stripe that appears on their [[Class 180]] units, re-painted the front ends (this making them look more like the non-buffered HSTs), and re-numbered the power cars into the four-hundreds. Grand Central's HSTs were cascaded to East Midlands Trains at the end of 2017.<ref>{{Cite news|url=http://www.pressreader.com/uk/rail-uk/20171220/281960313112051|title=Grand Central to replace HSTs with cascaded 180s|date=20 December 2017|work=Rail (UK)|access-date=6 January 2017}}</ref>

In February 2019 [[Hull Trains]] commenced using a First Great Western set between London King's Cross and Hull due to ongoing reliability issues with its Class 180s.<ref>HST enters service with Hull Trains ''[[Rail Express]]'' issue 265 April 2019 page 79</ref> A month later they introduced an additional set following further reliability issues. LNER withdrew its last InterCity 125s in December 2019.<ref>[https://web.archive.org/web/20191211194401/https://www.lner.co.uk/news/lner-bids-farewell-to-the-inter125-high-speed-train/ LNER Bids Farewell to the InterCity 125 High Speed Train] LNER 4 December 2019</ref>

===Midland Region===
On the London Midland Region, InterCity 125 trains were introduced later than on the other regions. They initially appeared on the former [[Midland Railway]] route from [[London St Pancras]] to [[Sheffield railway station|Sheffield]] and [[Nottingham railway station|Nottingham]]. Although they were initially not permitted to exceed {{convert|100|mi/h|km/h|abbr=on|sigfig=3}} on any part of the route, they still delivered time savings compared with the loco-hauled trains they replaced.{{citation needed|date=July 2017}}

The [[Midland Main Line]] received a series of speed improvements over the next two decades, until it became possible for HSTs to run at up to {{convert|110|mi/h|km/h|abbr=on|sigfig=3}} on some sections. An upgrade to the full {{convert|125|mi/h|km/h|abbr=on|sigfig=3}} was proposed by British Rail in the early 1990s, but because of privatisation this did not happen. However line improvements were completed in time for the spring 2014 timetable change, which has permitted 125&nbsp;mph running on some sections of the line and higher top speeds on others.{{citation needed|date=July 2017}}

Most long-distance services on this route have been transferred to new [[British Rail Class 222|Class 222 ''Meridian'']] diesel-electric multiple units, although many London services from {{rws|Nottingham}} still used the InterCity 125, as did all services from London St Pancras to {{rws|Leeds}}.<ref>{{cite news |url=http://www.railwaygazette.com/nc/news/single-view/view/demu-inspection-ensures-quality.html |title=DEMU inspection ensures quality |work=[[Railway Gazette International]] |location=London |date=1 March 2005 |access-date=18 May 2009 |archive-date=15 June 2011 |archive-url=https://web.archive.org/web/20110615132800/http://www.railwaygazette.com/nc/news/single-view/view/demu-inspection-ensures-quality.html |url-status=dead }}</ref><ref>{{cite press release | url= https://www.eastmidlandsrailway.co.uk/intercity | date= 17 March 2008 | title= Intercity Trains | publisher= [[East Midlands Railway]] | access-date= 27 August 2009 }}</ref> [[Midland Mainline (train operating company)|Midland Mainline]] inherited HSTs from BR after privatisation and operated them on its primary services at up to 110&nbsp;mph.

[[File:EMT HST 43058 Leicester AB1.JPG|thumb|right|[[East Midlands Trains]] liveried HST at [[Leicester railway station|Leicester]] in 2008]]

43089 also was returned to work on the mainline after being used in an experimental programme conducted by Network Rail and [[Hitachi]].<ref name = 'hybredhst' /> 43072, 43074 was transferred to [[East Coast (train operating company)|East Coast]] in 2012. Since December 2013, InterCity 125 sets have been permitted to operate at speeds of up to 125&nbsp;mph on certain parts of the routes from London St Pancras to Leeds and Nottingham.
[[File:43089 and 222005 South Wingfield.jpg|thumb|right|[[East Midlands Trains]] InterCity 125 passing a [[Class 222]] in 2009]]

On 15 May 2021, EMR retired their final two InterCity 125 trains, which were replaced by East Midlands Railway with {{brc|222}}, and had been displaced thanks to the introduction of {{brc|180}} and {{brc|360}} from [[Hull Trains]] and [[Greater Anglia]]. This made them the last HST operator to run InterCity 125 services to the capital.

===Cross-Country Route===
[[File:Cross Country (Inter City 125 branded) service departing Tamworth.jpg|thumb|[[CrossCountry]] (Inter City 125 branded) service departing [[Tamworth railway station|Tamworth]] in 2022]]
After privatisation, the [[Cross Country Route]] was operated by [[Virgin CrossCountry]], who replaced their InterCity 125 trains in the period 2002–2004 with [[Bombardier Voyager]] high-speed [[DMUs]].<ref>{{cite web|url=http://www.virgintrainsmediaroom.com/index.cfm?articleid=121 |title=New dawn for Virgin Trains |publisher=[[Virgin Group]] |date=13 June 2001 |access-date=18 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090619193546/http://www.virgintrainsmediaroom.com/index.cfm?articleid=121 |archive-date=19 June 2009 }}</ref> Most of the former Virgin CrossCountry fleet were stored for several years but a few ran on the [[Midland Main Line]] for the train company [[Midland Mainline (train operating company)|Midland Mainline]].

In 2007, the franchise passed to [[Arriva CrossCountry]]. In response to overcrowding, the company reintroduced five HST sets to supplement its Voyagers.<ref>{{cite press release |url=http://www.crosscountrytrains.co.uk/AboutCrossCountry/PressAndMedia/PressReleaseLaunch.aspx |title=New beginning for CrossCountry train travel |publisher=[[CrossCountry|Cross Country]] |date=11 November 2007 |access-date=18 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20091011105218/http://www.crosscountrytrains.co.uk/AboutCrossCountry/PressAndMedia/PressReleaseLaunch.aspx |archive-date=11 October 2009 }}</ref>

In September 2008, CrossCountry refurbished its first HST set {{ndash}} the coaches were refurbished to a similar "Mallard" standard as GNER trains, though their interior is in burgundy and there are fewer tables. They also differ from the East Coast sets in having electronic seat reservations, and the buffet car has been removed, with all catering provided at-seat from a catering base in coach B. Most of the coaches are rebuilt from loco-hauled Mark 3 stock. The refurbishment was carried out by Wabtec, [[Doncaster Works]]. Each set has had a TS removed, making them two power cars + seven coaches.<ref name="list" /> All coaches retained were fitted with automatic doors, toilets with controlled emission tanks and other accessibility modifications at Doncaster Works.

CrossCountry operated its last InterCity 125 service in September 2023.<ref>{{cite magazine |title=CrossCountry to withdraw its HST fleet by October |magazine=[[Rail Express]] |issue=323 |date=April 2023 |page=12}}</ref>

===West Coast and North Wales===
[[Virgin Trains West Coast]] HSTs regularly worked out of [[London Euston]] and [[Birmingham International railway station|Birmingham International]] to [[Holyhead railway station|Holyhead]] and [[Blackpool North railway station|Blackpool North]]. They also worked some Euston to [[Manchester Piccadilly]] services. Virgin's HSTs were re-deployed in May 2004. Due to there being numerous curves on the West Coast Main Line, the trains were not permitted to exceed 110&nbsp;mph on any part of the route.

When the [[West Coast Main Line]] was upgraded by [[Network Rail]] in the 2000s, it became necessary to operate diversionary routes whilst work was going on. As a result, [[Midland Mainline (train operating company)|Midland Mainline]] was asked by the then [[Strategic Rail Authority]] (SRA) to operate services from Manchester via the [[Hope Valley Line]] and Midland Main Line into {{Stnlnk|St Pancras}} while West Coast Main Line works took place. In a temporary operation dubbed ''[[Project Rio]]'',<ref name=regrio>{{cite web|url=http://www.rail-reg.gov.uk/upload/pdf/s22-mml_18thsa_reasons.pdf |title=Track access agreement between Network Rail and Midland Mainline |publisher=Track Access Executive |access-date=6 January 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080228103737/http://www.rail-reg.gov.uk/upload/pdf/s22-mml_18thsa_reasons.pdf |archive-date=28 February 2008 }}</ref> a large percentage of the stored Virgin CrossCountry power cars were overhauled and returned to service in an enlarged Midland Mainline fleet.<ref name = '125grp'/> Ending on 10 September 2004, the ''Project Rio'' fleet was gradually disbanded, with power cars moving to [[First Great Western]] and GNER.

{{anchor|Scotrail}}

===ScotRail Inter7City===
[[File:Inverkeithing - Abellio 43175-43143 (cropped).JPG|alt=ScotRail HST Inter7city|thumb|[[ScotRail]] HST Inter7city set in 2019]]
Twenty-six HST sets, nine with four coaches and 17 with five coaches, moved from Great Western Railway to [[Abellio ScotRail]] after being refurbished by [[Wabtec]] at [[Doncaster Works]] with new interiors, controlled emission tanks and automatic sliding doors. They operate on services from [[Edinburgh Waverley railway station|Edinburgh]] and [[Glasgow Queen Street railway station|Glasgow]] to [[Aberdeen railway station|Aberdeen]] and [[Inverness railway station|Inverness]], as well as between Aberdeen and Inverness.<ref>"Quality and more trains key to Abellio's SR franchise" ''[[Rail (magazine)|Rail]]'' issue 760 29 October 2014 page 10</ref><ref>"More Details of SR HSTs" ''[[Today's Railways UK]]'' issue 181 January 2017 page 67</ref> The first set entered service in October 2018.<ref name=":0">{{Cite news|url=http://railcolornews.com/2018/10/16/uk-scotrail-starts-inter7city-revenue-service-with-refurbished-hst/|title=Scotrail starts Inter7City service with refurbished HSTs|last=Lissenberg|first=Ferry|date=16 October 2018|work=Railcolor|access-date=18 October 2018|language=en-GB}}</ref> ScotRail's HST fleet operates under the brand name ''Inter7City.''

In September 2024, the Scottish Government announced their intention to replace ScotRail's HST fleet.<ref>{{Cite web |date=3 September 2024 |title=ScotRail's old high-speed trains to be replaced |url=https://news.stv.tv/scotland/scotrails-old-high-speed-trains-to-be-replaced |access-date=3 September 2024 |website=STV News |language=en-GB}}</ref>

===Network Rail===
{{Main|New Measurement Train}}
[[File:Tamworth railway station MMB 27 43062 (cropped).jpg|thumb|The [[New Measurement Train]] on the [[West Coast Main Line]] in 2011]]
One specially converted HST set is in service with [[Network Rail]], assessing the condition of [[Rail tracks|track]] so that engineers can determine where to work. The train is painted in the yellow livery used for maintenance vehicles, and often referred to as the "flying banana"<ref name="banana-ref-1">{{cite web |title=New Measurement Train (NMT) |url=https://www.networkrail.co.uk/running-the-railway/looking-after-the-railway/fleet-machines-vehicles/new-measurement-train-nmt/ |archiveurl=https://web.archive.org/web/20190219162702/https://www.networkrail.co.uk/running-the-railway/looking-after-the-railway/fleet-machines-vehicles/new-measurement-train-nmt/ |archivedate=19 February 2019 |accessdate=19 February 2019 |website=Network Rail |quote=Affectionately known as the Flying Banana due to its distinctive yellow livery |location=London}}</ref> (a nickname that was originally applied to the whole class because when first introduced by BR they wore a predominantly yellow livery).{{Citation needed|date=September 2024}} The set is the [[New Measurement Train]].<ref>{{cite news| url=http://www.highbeam.com/doc/1G1-107756324.html | archive-url=https://web.archive.org/web/20121025150305/http://www.highbeam.com/doc/1G1-107756324.html | url-status=dead | archive-date=25 October 2012 | date=1 August 2003 |title= Network Rail, Britain, has unveiled its new 200km/h measurement train |work=International Railway Journal | access-date=18 May 2009}}</ref>

Another single engine, 43089, was used in tests on hybrid battery powered vehicles in collaboration with [[Hitachi]].<ref name = 'hybredhst'>{{cite news | url=http://findarticles.com/p/articles/mi_m0BQQ/is_6_47/ai_n19313548/ |date = June 2007 |title= Hitachi reveals 200km/h hybrid HST |work=International Railway Journal | access-date=18 May 2009}}</ref><ref>{{cite web|url=http://www.jbce.org/files/hitachipresentation.pdf |title=Towards Sustainable Technology in Transport Sector |publisher=[[Hitachi]] |access-date=18 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20080516004125/http://www.jbce.org/files/hitachipresentation.pdf |archive-date=16 May 2008 }}</ref>

==Numbering and formation==
{{See also|British Rail Class 43 (HST)|British Rail Mark 3}}
British Rail considered the InterCity 125 sets to be [[diesel multiple unit]]s because they were fixed formation trains. They were allocated British Rail Class 253 (2+7 sets allocated to Western Region depots for use on Western Region and Cross-Country services) and Class 254 (2+8 sets allocated to the Eastern and Scottish Regions for use on the East Coast Main Line), the prototype train having been Class 252.  Therefore, each set was allocated a set number (253 xxx or 254 xxx), which was carried on the front of the power cars.  Individual vehicles were numbered in the 4xxxx series (see table below) and, because they were regarded as multiple unit vehicles, also had regional prefixes according to their allocated depot (E for Eastern Region, SC for Scottish and W for Western); this included the power cars as well as the trailers.

With power cars often requiring maintenance more frequently than the trailer cars, power car swaps soon began to take place; there were a few spare power cars to allow for this.  This often resulted in different set numbers being displayed at each end of the same train.  As a result, during the early 1980s the power cars began to be regarded as "loose", and the use of set numbers for the whole train was abandoned.  The trailer cars remained in fixed formations, however, and still allocated a set number of sorts, although that was not displayed anywhere.

As sectorisation began to take hold during the mid-1980s, the use of regional prefixes on coaches and multiple unit vehicles was discontinued.  At about the same time it was decided to reclassify the InterCity 125 trains (the hyphen having been dropped by the new InterCity sector) as locos and coaches.  To avoid renumbering the power cars, they became [[British Rail Class 43 (HST)|British Rail Class 43]] diesel locos, although a space was never inserted between the second and third digits (as was common practice on other locos at the time, e.g. 47 401).

The vehicle types used to form High Speed Trains are listed below:<ref>The individual units (carriages and power cars) were all numbered in the 4xxxx carriage series set aside for HST and [[Advanced Passenger Train]] vehicles. Numbers followed those allocated to the prototype [[British Rail Class 252]] unit, so power cars were numbered from 43002 upwards</ref>

{| class="wikitable"
|----- bgcolor=#f9f9f9
! rowspan="2" |&nbsp;Class&nbsp;
! rowspan="2" |Image
! rowspan="2" |&nbsp;Type&nbsp;
! colspan="2" |&nbsp;Top speed&nbsp;
! rowspan="2" |&nbsp;Number&nbsp;
! rowspan="2" |&nbsp;Built&nbsp;
! rowspan="2" |&nbsp;Notes&nbsp;
|----- bgcolor=#f9f9f9
!&nbsp;mph&nbsp;
!&nbsp;km/h&nbsp;
|-
|[[British Rail Class 43 (HST)|Class 43]]
|[[File:EMT HST 43058 Leicester AB1.JPG|100px]]
|[[Diesel locomotive]]
| rowspan="2" |125
| rowspan="2" |201
|197
|1975–1982
|2 InterCity 125 power cars, operated in Top and Tail formation. 
|-
|[[British Rail Mark 3|Mark 3 Coach]]
|[[File:British Rail Mk 3 M12043 at Marylebone A.jpg|100px]]
|[[Passenger railroad car|Passenger coaching stock]]
|848
|1975–1988
|British Rail's third fundamental design of passenger coach, developed primarily for the InterCity 125. 
|}

{| class="wikitable"
!colspan=3|Coach number
|-
!Number Range
!Type
!Notes
|-
|400xx
|Trailer Buffet (TRSB)
|Renumbered 404xx in 1983; some converted to 402xx series
|-
|403xx
|Trailer Buffet (TRUB)
|All converted to 407xx series (first class)
|-
|405xx
|Trailer Kitchen (TRUK)
|All withdrawn and converted for other uses
|-
|41xxx
|Trailer First (TF)
| rowspan="2" |Majority in service, some converted or scrapped
|-
|42xxx
|Trailer Second (TS)
|-
|43002-43198
|Driving Motor (Brake) (DM or DMB)
|Majority in service, three scrapped after accidents<br />These are now classified as [[British Rail Class 43 (HST)|British Rail Class 43]]
|-
|44000-44101
|Trailer Guard Second (TGS)
|Majority in service, some converted
|-
|}

The 197 production series power cars were numbered 43002–43198.  43001 was applied to the second of the two prototype power cars, while the first of the pair (now preserved as part of the National Collection) became 43000 – unusual because BR [[TOPS]] classification numbered its locomotives from 001 upwards (this was because it was not, at the time, classified as a locomotive).  Subsequently, on fitting of new engines, power cars operated by the InterCity East Coast and Cross Country franchisees have been renumbered in the 432xx or 433xx series (by adding 200 to their serial numbers), while Grand Central also changed the third digit of its power cars to 4 (by adding 300 or 400).

The renumbering of the 400xx series catering vehicles in 1983 was to avoid their numbers clashing with the Class 40 diesel loco fleet (numbered 40 001 to 40 199) when BR's loco (TOPS) and coaching stock number series were merged.

In 2002, Class 255 was allocated for the reformation of some HST power cars and trailers into semi-fixed formation trains, to be known as Virgin ''Challenger'' units, for use by [[Virgin CrossCountry]]. These formations would have had power cars sandwiching one Trailer First, a Trailer Buffet, two Trailer Seconds and a Trailer Guard Second. These plans came to naught as the [[Strategic Rail Authority]] planned to transfer most of the stock to [[Midland Mainline (train operating company)|Midland Mainline]] for its 'Rio' services between London and Manchester.<ref name = '125grp'>{{cite web | url=http://www.125group.org.uk/index.php?module=htmlpages&func=display&pid=9 |title= Privatisation 1993–2005 | publisher= 125group.org.uk | access-date=19 May 2009}}</ref>

=== Livery ===
[[File:Intercity 125 original logo.svg|thumb|InterCity logo 1978–1985]]
{{See also|British Rail corporate liveries}}
[[File:43005 Reading 2004.png|thumb|[[First Great Western]] HST at [[Reading railway station]] in 2004, wearing two liveries: "Fag Packet" on the power car and "Barbie" on the coaches]]

The original "Inter-City 125" livery was blue and grey, with a yellow front to improve visibility which continued down the side of the power cars.<ref>{{cite book| author= Morrison, Gavin | publisher = Ian Allan | year= 2007| title= Heyday of the HST | page = foreword |isbn= 978-0-7110-3184-5}}</ref><ref>{{cite web|url=http://www.doublearrow.co.uk/manual/4_19.1977-08.jpg |archive-url=https://archive.today/20130420023927/http://www.doublearrow.co.uk/manual/4_19.1977-08.jpg |url-status=dead |archive-date=20 April 2013 |title=BR livery HST 4/19 C.I.M. |publisher=BR |access-date=3 December 2013 }}</ref>

The second livery had mostly grey power-cars with a white band along the middle, yellow underneath the white band, with the InterCity colours (cream, red, white, brown) for the parcel compartment of the power cars and the coaches.

There was brownish-grey, dark grey (almost black) around the windows with a red and white stripe below the windows, and retaining the yellow bands on the power cars. The final variant of this livery saw the yellow side-bands replaced with white and did not feature the British Rail name or logo: it carried the new sector branding [[InterCity (British Rail)|Intercity logo]] in serif type and an image of a flying swallow.<ref name=mark1>{{cite book | last = Parkin | first = Keith | title = British Railways Mark 1 coaches | publisher = The Historical Model Railway Society | year = 2006 | edition= Revised | pages= 67–73 |isbn = 0-902835-22-X}}</ref><ref>{{cite web|url=http://www.modelrailwaysdirect.co.uk/acatalog/Hornby-R2702X.html |title=BR InterCity Executive HST 125 High Speed Train |publisher=Model Railways Direct |access-date=18 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090107003115/http://www.modelrailwaysdirect.co.uk/acatalog/Hornby-R2702X.html |archive-date=7 January 2009 }}</ref> This is commonly referred to as "InterCity Swallow" livery, and was applied to other locomotives in the sector.

After the [[privatisation of British Rail]], train operating companies painted the HSTs in their own colour schemes, with some lasting longer than others.<ref>{{cite web | url=http://www.therailwaycentre.com/Pages%20Loco/Recognition%20loco/Illus_43A%20HST.html | archive-url=https://web.archive.org/web/20030404191622/http://www.therailwaycentre.com/Pages%20Loco/Recognition%20loco/Illus_43A%20HST.html | url-status=usurped | archive-date=4 April 2003 |title= Examples of different liveries on HSTs |publisher=therailwaycentre.com | access-date=18 May 2009}}</ref>

Two of [[Great Western Railway (train operating company)|Great Western Railway]]'s powercars have been repainted into heritage liveries; 43002 has repainted into original InterCity 125 Blue & Yellow livery whereas 43185 has been repainted into InterCity Swallow livery.

Two powercars [43046 and 43055] owned by [[Locomotive Services Limited]] have been repainted into [[Blue Pullman]] colours.<ref>{{Cite web|title=Railway Herald :: Blue Pullman takes to the rails in November|url=http://railwayherald.com/uknews/blue-pullman-takes-to-the-rails-in-november|access-date=30 October 2020|website=railwayherald.com}}</ref> The units will be used for railtour services operated by LSL beginning on 14 November 2020.<ref>{{Cite tweet|user=mrtimdunn |number=1288963589911580674 |title=Statesman Rail is repainting a HST set into Nanking Blue|access-date=30 October 2020|date=30 July 2020|language=en}}</ref>

==Cultural impact==

===Public reaction===
The Intercity service proved an instant hit with the British public.<ref>{{cite news |url= https://news.bbc.co.uk/1/hi/england/berkshire/5407016.stm |title= High Speed Train marks 30 years |work=BBC News |access-date=29 April 2009 |date=4 October 2006 |first=Joe |last=Campbell}}</ref> By the early 1980s the HST had caught the travelling public's imagination,<ref>{{cite news |url= http://nl.newsbank.com/nl-search/we/Archives?p_product=AT&p_theme=at&p_action=search&p_maxdocs=200&p_topdoc=1&p_text_direct-0=0EB7C1B025A01C5A&p_field_direct-0=document_id&p_perpage=10&p_sort=YMD_date:D&s_trackval=GooglePM |date=8 September 1985 |title= Both English, French trains getting fancy |newspaper=The Atlanta Journal-Constitution |access-date=29 April 2009}}</ref><ref>{{cite news |author= Mitchell, Alan |url= http://www.accessmylibrary.com/coms2/summary_0286-5461214_ITM |title= Train of Thought |work=Marketing |publisher= Haymarket Business Publications |access-date=29 April 2009 |date=8 March 1990}}</ref> thanks in part to a television advertising campaign fronted by entertainment personality [[Jimmy Savile]], together with the advertising strap-line "[[The Age of the Train|This is the age of the train]]".<ref>{{cite news |last1=Wake |first1=Tony |title=Rod Allen Advertising 'jingle king' (obituary) |url= https://www.independent.co.uk/news/obituaries/rod-allen-402337.html |access-date=14 February 2015 |work=[[The Independent]] |location= London |date=14 September 2007}}</ref><ref>An example of this advertising campaign can be found through online video sites such as [https://www.youtube.com/watch?v=D4CybduRq2k YouTube].</ref> British Rail enjoyed a boom in patronage on the routes operated by the HSTs and InterCity's revenues increased, although the total was not enough to remove the need for subsidies to British Rail.<ref>{{cite book| last= Harris |first=Sim | publisher = Ian Allan | year= 2016| title= The Railway Dilemma | page = 16 | isbn = 978-0-7110-3835-6 }}</ref>

===International interest===
The success of the HST had significant international impact. Foreign press for decades observed and praised the speed and quality of the service.<ref>{{cite news |url= https://www.nytimes.com/1987/09/24/opinion/l-can-railroads-come-back-at-high-speed-320087.html |title= Can railroads come back at high speed? (Letter to the editor) |author= Gottlieb, A. Harold |newspaper=The New York Times |access-date=29 April 2009 |date=24 September 1987}}</ref>

The InterCity 125 was used as a case study for evaluating the potential for a [[California High-Speed Rail|high-speed rail]] system in [[California]].<ref>{{cite web|url=http://www.uctc.net/papers/114.pdf |title=British Rail's InterCity 125 and 225 |author=Barnett, Roger |publisher=University of California Transportation Centre |access-date=17 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20080529152114/http://www.uctc.net/papers/114.pdf |archive-date=29 May 2008 }}</ref> In Australia, it was used as the base for developing the [[New South Wales XPT|XPT]], in cooperation with British Rail.

===Models===
[[File:N Scale - HST 125 Inter City - GB - IMG 0029.jpg|thumb|[[British Rail Class 253|Class 253]] Del Prado N Gauge scale BR Class 43 (HST) HST power car model]]
There have been many model and toy guises of the IC125.<ref>{{cite web|url=http://www.themodeller.com/Products/BR-Intercity-125-High-Speed-Train---Train-Pack__HOR-R2701X.aspx |title=Example of a model Intercity 125 |website=themodeller.com |archive-url=https://web.archive.org/web/20090505224047/http://www.themodeller.com/products/BR-Intercity-125-High-Speed-Train---Train-Pack__HOR-R2701X.aspx |archive-date=5 May 2009 |url-status=dead}}</ref> One of the first in the UK was by [[Hornby Railways]], which launched its first model version as a train set in 1977.<ref>{{cite web|url=http://www.hornbyguide.com/item_year_details.asp?itemyearid=1098|title=Hornby 1977 - B.R. High Speed Train Set|work=Hornby Railways Collector Guide|access-date=7 August 2024|archive-date=14 May 2020|archive-url=https://web.archive.org/web/20200514204628/http://www.hornbyguide.com/item_year_details.asp?itemyearid=1098|url-status=live}}</ref><ref>{{cite web|url=https://www.hornby.com/us-en/shop/locomotives/locomotives-by-class/hst-class-43.html|title=HST - InterCity 125 (Class 43)|work=Hornby official website|access-date=6 August 2024|archive-date=14 May 2020|archive-url=https://web.archive.org/web/20200514212257/https://www.hornby.com/us-en/shop/locomotives/locomotives-by-class/hst-class-43.html}}</ref> This model was supplied with an incorrect length BR Mk3 Open 2nd coach which was shortened to allow the model to reliably negotiate the smallest radius curves. This was done by removing one of the 8 side windows rather than scaling the whole length. In 2025, as part of the ''Railway 200'' celebrations, Hornby reproduced a retro replica of their first ever Hornby Railways, B.R Inter-City 125 High Speed Train set from 1977.<ref>{{cite web|url=https://uk.hornby.com/products/hornby-railways-br-high-speed-retro-train-set-r1289m |work=[[Hornby Railways|Hornby]]|title=R1289M Hornby Railways B.R. High Speed Retro Train Set|access-date=23 August 2025|archive-date=23 August 2025|archive-url=https://web.archive.org/web/20250823172934/https://uk.hornby.com/products/hornby-railways-br-high-speed-retro-train-set-r1289m|url-status=live}}</ref> In 1978 Hornby Railways issued an additional BR Mk 3 Open 2nd coach,<ref>{{cite web|url=http://www.hornbyguide.com/item_details.asp?itemid=141|title= Hornby 1978 -B.R. Mk III Inter-City Open 2nd|work=Hornby Railways Collector Guide|access-date=16 February 2020}}</ref>
followed by their first model of a BR Mk 3 Open 1st Coach in 1979<ref>{{cite web|url=http://www.hornbyguide.com/item_details.asp?itemid=339|title= Hornby 1979 -Mk III Inter-City Open 1st|work=Hornby Railways Collector Guide|access-date=16 February 2020}}</ref> and a BR Mk 3 Restaurant Buffet Car (TRUB) in 1980.<ref>{{cite web|url=http://www.hornbyguide.com/item_details.asp?itemid=142|title=Hornby 1980 - B.R. Mk.3 Restaurant Buffet Car (TRUB)|work=Hornby Railways Collector Guide|access-date=16 February 2020}}</ref> The incorrect seven side windows was corrected to eight windows in 1985 when Hornby made modifications to the tooling for the BR Mk 3 (TS) and (TF) coaches.<ref>{{cite web|url=http://www.hornbyguide.com/year_category_images.asp?categoryid=5&yearid=25|title=1985 Passenger Rolling Stock Images|work=Hornby Railways Collector Guide|access-date=4 March 2022}}</ref> It was later released in InterCity 'Swallow' livery, [[First Great Western|Great Western]] green-and-white, [[Midland Mainline (train operating company)|Midland Mainline]] and [[Virgin Trains]].  [[Lima (models)|Lima]] released its version of the IC125 in 1982, of which the Mark 3 coaches were correct to the lengths of the real-life coaches and included the guard's coach. Hornby eventually followed suit in the late-1990s, when its short Mark 3 coaches were replaced by correct scale length ones but omitted the guard's coach. In 2006 Hornby released for the first time a modified tooling BR Mk 3 (TGS) Coach.<ref>{{cite web|url=http://www.hornbyguide.com/item_details.asp?itemid=2989|title=Hornby B.R. Mk3 Trailer Guards Standard Coach 2006|work=Hornby Railways Collector Guide|access-date=4 March 2022}}</ref> In 2008 after acquiring tooling from ex-Lima rolling stock which then became the Hornby RailRoad range. Hornby released in a variety of different liveries both BR and post-privatisation a newly tooled super-detailed Class 43 powers car,<ref>{{cite web|url=http://www.hornbyguide.com/item_year_details.asp?itemyearid=10717|title=2008 - B.R. Intercity 125 High|work=Hornby Railways Collector Guide|access-date=6 April 2020}}</ref> alongside the more basic Class 43 HST power cars of the Railroad Range.<ref>{{cite web|url=http://www.hornbyguide.com/item_year_details.asp?itemyearid=10877|title=2008r - Virgin HST Pack (Class 43)|work=Hornby Railways Collector Guide|access-date=6 April 2020}}</ref> In 2009 Hornby released newly tooled BR Mk 3 coaches.<ref>{{cite web|url=http://www.hornbyguide.com/year_category_images.asp?categoryid=5&yearid=91|title=Hornby 2009 Passenger Rolling Stock Images|work=Hornby Railways Collector Guide|access-date=6 April 2020}}</ref> Graham Farish were the first to produce an HST in N gauge; more recently Dapol have produced another N gauge model of the train.  Railway Shop (Hong Kong) produces a T gauge model (1:450 scale).

==Developments and changes==
[[File:43116 at waverley.jpg|thumb|An InterCity 125 with a [[Paxman Valenta]] engine, which produced a lot more noise and exhaust gases than its replacements]]

===Damaged vehicles and accidents===

{{update-section|date=August 2020}}

Five [[British Rail Class 43 (HST)|Class 43]] locomotives have been written off in railway accidents, three of which occurred on the [[Great Western Main Line]]. 43011 was written off in the 1999 [[Ladbroke Grove rail crash]], 43019 was written off after colliding with a car at [[Ufton Nervet rail crash|Ufton Nervet]] in 2004 and 43173 was scrapped after heavy damage in the [[Southall rail crash]] of 1997. In each of these cases, the damage was to the leading power car; the trailing power cars suffered limited or no damage and were returned to service. At Ladbroke Grove and Ufton Nervet, the accidents were ultimately caused by factors not involving the HST sets or their drivers, although the set involved in the Ladbroke Grove crash had a faulty AWS system;<ref>{{cite book |url=http://www.rail-reg.gov.uk/upload/pdf/incident-ladbrokegrove-lgri1-optim.pdf |title=The Ladbroke Grove Rail Inquiry – Part 1 Report |year=2001 |isbn=0-7176-2056-5 |publisher=Health and Safety Commission |access-date=1 March 2012 |url-status=dead |archive-url=https://web.archive.org/web/20090325165337/http://www.rail-reg.gov.uk/upload/pdf/incident-ladbrokegrove-lgri1-optim.pdf |archive-date=25 March 2009 }}</ref><ref>{{cite web|url=http://www.rssb.co.uk/SiteCollectionDocuments/pdf/reports/Ufton%20-%20Preliminary%20Report.pdf |title=Preliminary report into railway accident at Ufton Nervet |publisher=Rail Safety and Standards Board |date=25 January 2005 |access-date=1 March 2012 }}{{dead link|date=May 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> however, the Southall accident was due to the HST colliding with a goods train which was entering Southall Goods Yard, crossing the main lines. The immediate cause of the crash was the result of the driver of the HST [[Signal passed at danger|passing a red signal without stopping]]. In addition, the leading power car of the set had a faulty [[Automatic Warning System]] which if operational would have alerted the driver to his error and possibly prevented the accident.<ref>{{cite web|url=http://www.rail-reg.gov.uk/upload/pdf/incident-southall-hscprogressfeb02.pdf |title=The Southall rail accident inquiry report: Summary of progress |date=February 2002 |publisher=Health and Safety Commission |access-date=1 March 2012 |url-status=dead |archive-url=https://web.archive.org/web/20070930223049/http://www.rail-reg.gov.uk/upload/pdf/incident-southall-hscprogressfeb02.pdf |archive-date=30 September 2007 }}</ref> Following investigation, this system has since been required to be kept operational and switched on for all use of the InterCity 125 fleet.

An InterCity HST, comprising four coaches between [[British Rail Class 43 (HST)|Class 43]] power cars 43030 and 43140, was involved in the [[Stonehaven derailment]] on 12 August 2020, in which three people died.<ref name="BBC-53751678">{{Cite news|date=12 August 2020|title=Major emergency response after train derails |work=BBC News|url=https://www.bbc.com/news/uk-scotland-north-east-orkney-shetland-53751678|access-date=12 August 2020}}</ref><ref name="BTP">{{cite web |title=Three people have sadly died following train derailment - Scotland |url=https://media.btp.police.uk/r/17325/three_people_have_sadly_died_following_train_dera |archive-url=https://web.archive.org/web/20200812172845/https://media.btp.police.uk/r/17325/three_people_have_sadly_died_following_train_dera |url-status=dead |archive-date=12 August 2020 |publisher=British Transport Police |access-date=12 August 2020 }}</ref> Both power cars were scrapped following the subsequent investigation.<ref>{{cite magazine |title=NR recovers wrecked vehicles from Carmont crash |magazine=Rail |publisher=Bauer Media Group |location=Peterborough |issue=914 |date=23 September 2020 |page=6 |issn=0953-4563 }}</ref><ref>{{cite magazine |title= Carmont accident Mk3s and a power car scrapped |magazine=[[Rail Magazine]] |issue=931 |date=19 May 2021| page=25}}</ref><ref>{{cite magazine |title= HST Power Car Round Up |magazine=[[Railways Illustrated]] |issue=240 |date=February 2023| page=19}}</ref>

===Re-engining and refurbishment===
[[File:First Great Western Refreshed HST B2 TF 41052 Interior.JPG|thumb|Refurbished Mark 3 coach First Class interior (First Great Western)]]
{{Main|British Rail Class 43 (HST)#Life extension}}
In 2005, the train leasing company [[Angel Trains]] initiated and led an industry-wide programme to replace the 30-year-old [[Paxman Valenta]] engines in the HST power cars with new [[MTU Friedrichshafen|MTU]] 16V 4000 engines.<ref>{{cite press release |url=http://www.angeltrains.co.uk/Press/release.aspx?Id=553 |title=Clear plans for the future of the HST fleet |publisher=[[Angel Trains]] |access-date=18 May 2009 |archive-date=25 May 2006 |archive-url=https://web.archive.org/web/20060525070713/http://www.angeltrains.co.uk/press/release.aspx?Id=553 |url-status=dead }}</ref>  The upgrade, which was part of a £110{{nbsp}}million total investment made by Angel Trains on its fleet of High Speed Trains, included the re-powering and refurbishment of 54 HST power cars; this included those then on lease to GNER (23),<ref>{{cite news |url= http://www.yorkshirepost.co.uk/news/GNER39s-highspeed-trains-to-become.1524286.jp |title= GNER's high-speed trains to become lean, green machines |date=25 May 2006 |author= Dooks, Brian |newspaper=Yorkshire Post |location=Leeds |access-date=29 April 2009}}</ref> [[First Great Western]] (26) and [[CrossCountry]] (5). Virgin CrossCountry planned a similar project in the early 2000s but, with the collapse of the programme, the upgraded trainsets were sold along with their unmodified stablemates.

Additionally, many operators undertook some refurbishment of the Mark 3 coaches in the early 2000s. In view of the delay and change of direction of the [[HST2]] programme,<ref>{{cite news | url=http://www.accessmylibrary.com/coms2/summary_0286-11827022_ITM |title=State leads Britain's high speed train replacement strategy |work= [[Railway Gazette International]] |access-date=18 May 2009 | date=November 2005 }} {{Dead link|date=April 2012|bot=RjwilmsiBot}}</ref> operators began to refurbish their HST fleets in 2006; both by remotoring with the more modern MTU4000 diesel engine,<ref>{{cite web | url=http://www.railwaypeople.com/rail-news-articles/fitting-the-mtu-power-unit-into-the-hsts-1589.html |title= Fitting the MTU power unit into the HSTs |publisher=railwaypeople.com | access-date=18 May 2009}}</ref> and by refurbishing the coach interiors.<ref>{{cite web |url = https://www.youtube.com/watch?v=_dKEviqeFrU |title = Official video by First Great Western documenting the refurbishment programme |date = 2 August 2008 |publisher = Youtube.com |access-date = 6 September 2009}}</ref> It was anticipated that these overhauls would give the HST at least another 10{{nbsp}}years in front-line service.<ref>{{cite news | url=http://www.accessmylibrary.com/coms2/summary_0286-31894764_ITM |title=A refreshing change! First Great Western's InterCity 125 fleet looked tired and old-fashioned — but a radical upgrade means these 30-year-old trains are now better than ever |work=International Railway Journal |date=1 July 2007 |access-date=28 April 2009}}</ref>

===Replacements===
The first partial replacement of HSTs occurred from 1988 on the [[East Coast Main Line]], with the introduction of the [[InterCity 225]] when the line to Edinburgh was electrified.<ref>{{cite news |url= https://news.bbc.co.uk/2/hi/uk_news/976815.stm |title= Intercity 225: Fastest in the fleet |work=BBC News |access-date=28 April 2009 |date=17 October 2000}}</ref> Some were retained for services to Aberdeen, Inverness, Skipton, Bradford and Hull.

As the InterCity 125 fleet aged, it became increasingly recognised that the train was nearing the end of its service life.<ref>{{cite news |url= https://www.theguardian.com/world/2004/oct/18/transport.uk |title=InterCity 125 nears the end of the line |author= Clark, Andrew |newspaper=The Guardian |date=18 October 2004 |access-date=28 April 2009 |location=London}}</ref> More recently, HSTs have been replaced (or augmented) by high-speed [[Diesel multiple units]] (DMUs), such as the [[Bombardier Voyager]]s and the UK express version of the [[Alstom Coradia]]. These DMUs have better acceleration than the HST, due to a higher power/weight ratio, with greater efficiency and braking performance.<ref>{{cite web |url=http://www.networkrail.co.uk/browse%20documents/StrategicBusinessPlan/Other%20supporting%20documents/Rolling%20stock%20(Final).pdf |date=October 2007 |title=Strategic Business Plan: Rolling Stock paper |publisher=[[Network Rail]] |access-date=18 May 2009 |archive-url=https://web.archive.org/web/20081030202249/http://www.networkrail.co.uk/browse%20documents/StrategicBusinessPlan/Other%20supporting%20documents/Rolling%20stock%20(Final).pdf |archive-date=30 October 2008 |url-status=dead }}</ref>

In 2005, the initial concept of [[HST2]] was rejected by the government and the rail industry as a like-for-like replacement for the HST fleet.<ref>{{cite news |url= http://www.accessmylibrary.com/coms2/summary_0286-13931097_ITM |title=Experts cast doubt over rail revolution |publisher=Europe Intelligence Wire |access-date=18 May 2009 | date=16 March 2006 }}</ref> In the light of this rejection, in 2006, existing operators turned to refurbishments of the InterCity 125 trains. Nevertheless, the HST2 concept was expanded and replaced by the [[InterCity Express Programme]], with proposals for a joint replacement of both HST and [[InterCity 225]] trains.<ref>{{cite news | url=http://www.railway-technology.com/projects/intercityexpress/ |title=Intercity Express Programme, United Kingdom |publisher=railway-technology.com |access-date=28 April 2009}}</ref> The eventual successor to the two InterCity fleets is the [[Hitachi Super Express]],<ref name="RGI0902AT">{{cite news |url=http://www.railwaygazette.com/news_view/article/2009/02/9359/agility_trains_to_supply_super_express_fleet.html |title=Agility Trains to supply Super Express fleet |date=12 February 2009 |access-date=12 February 2009 |location=London |work=[[Railway Gazette International]] |archive-date=13 February 2012 |archive-url=https://web.archive.org/web/20120213183821/http://www.railwaygazette.com/news/single-view/view/agility-trains-to-supply-super-express-fleet.html |url-status=dead }}</ref> comprising three classified types of fixed-rake formations: two [[electro-diesel]] types, the [[British Rail Class 800|Class 800]] sets and the [[British Rail Class 802|Class 802]] sets, and the [[electric multiple unit]] [[British Rail Class 801|Class 801]] sets.

On the [[Greater Western franchise]], the first HST was returned to its leasing company in September 2017; by June 2019, all sets on inter-city routes were withdrawn in favour of the [[British Rail Class 800|Class 800]] and the [[British Rail Class 802|Class 802]] sets.<ref name=Rail010917>[http://www.railmagazine.com/news/fleet/first-hst-for-scotrail-arrives-in-scotland First HST for ScotRail arrives in Scotland] ''Rail Magazine'' 1 September 2017</ref><ref>{{Cite web|url=https://www.railmagazine.com/news/fleet/great-western-railway-calls-time-on-long-distance-hsts|title=Great Western Railway calls time on long-distance HSTs|website=www.railmagazine.com}}</ref>

===Sewage discharge===
In the UK, train operators are allowed legally to discharge up to 25 litres of untreated waste at a time on to the track.<ref>{{cite web|url=https://www.gov.uk/guidance/waste-exemption-d2-depositing-waste-from-a-railway-sanitary-convenience|title=Waste exemption: D2 depositing waste from a railway sanitary convenience|website=GOV.UK |date=July 2025 }}</ref> Most Mk3 coaches have no toilet tanks, discharging directly onto the track. In the 2000s, both the [[National Union of Rail, Maritime and Transport Workers|RMT]] trade union and politicians were concerned at the environmental impact of this legacy issue. The problem was first raised in 2003, after [[Railtrack]] staff at {{stnlnk|Nottingham}} abandoned local clean-up and then track maintenance procedures due to an excessive buildup of sewage waste in the area.<ref>{{cite news |url= https://news.bbc.co.uk/2/hi/uk_news/3020938.stm |title= Toilet waste 'hampers rail repairs' |author= Geoghegan, Tom |work=BBC News |date=24 July 2003 |access-date=13 November 2013}}</ref> In 2006 the RMT agreed waste-tank and clean-out developments at [[Northern Rail]]'s [[Heaton TMD|Heaton depot]] in 2006 with GNER, plus new clean-out procedures at all other depots, to solve an ongoing dispute over the previous 18 months.<ref>{{cite news |url= https://news.bbc.co.uk/1/hi/england/5249982.stm |title=Toilet waste 'sprays' track staff |work=BBC News |date=6 August 2006 |access-date=13 November 2013}}</ref>

By 2011, the [[European Union]] had started a formal investigation to see whether trains composed of such coaches were breaking EU environmental and health laws, although the [[Environment Agency]] confirmed that train companies claimed special exemptions to dump waste along the tracks.<ref>{{cite news |url= http://www.thesundaytimes.co.uk/sto/news/uk_news/Environment/article503796.ece |archive-url= https://web.archive.org/web/20131113180849/http://www.thesundaytimes.co.uk/sto/news/uk_news/Environment/article503796.ece |url-status= dead |archive-date= 13 November 2013 |title= Rail bosses face EU inquiry over sewage on tracks |author1=Ungoed-Thomas, Jon |author2=Clover, Charles |work=The Sunday Times |location= London |date=9 January 2011 |access-date=13 November 2013}} {{subscription required}}</ref> In 2013, transport minister [[Susan Kramer]] branded the practice "utterly disgusting" and called on the industry to take action. [[Association of Train Operating Companies|ATOC]] responded by stating that, as all new vehicles had to be fitted with compliant toilet tanks, with withdrawal of the HSTs by the end of 2017 the problem would be solved.<ref>{{cite news |url= https://www.bbc.co.uk/news/uk-politics-24925280 |title=End 'disgusting' train toilet sewage – Lady Kramer |work=BBC News |date=13 November 2013 |access-date=13 November 2013}}</ref> HSTs remained in operation after 2017, but sliding-door conversions of CrossCountry's fleet and the shortened sets for GWR and ScotRail have all included the fitting of controlled emission toilets.<ref>{{cite web |url=http://railnews.mobi/news/2017/10/23-intercity-expresses-back-in-service.html |title=InterCity Expresses return to service on GWR |date=23 October 2017}}</ref><ref>{{cite web |url=https://www.railmagazine.com/trains/current-trains/how-the-hsts-are-being-transformed-for-scottish-services |title=How the HSTs are being transformed for Scottish services |date=13 February 2018}}</ref>

===Obsolescence factors===
In 2019, HSTs were not permitted to operate passenger services on the [[National Rail]] network in their original form because various deficiencies made them non-compliant with accessibility regulations – in particular, the need to open doors manually. However, to avoid rolling stock shortages, some operators were granted temporary permission to operate them, namely [[Abellio ScotRail|ScotRail]], whose sets were planned to be modified,<ref>{{Cite web|url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/855400/scotrail-short-form-hsts-2020-dispensation-letter-timed.pdf|title=The Railways (Interoperability) Regulations 2011 – Abellio Scotrail HST sets - 2020 accessibility deadline|date=19 December 2019 }}</ref> and East Midlands Trains, who have since withdrawn their sets in favour of [[Class 222]] ''Meridians''.<ref>{{Cite web|url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/855329/emt-lner-pb-hst-dispensation-letter.pdf|title=The Railways (Interoperability) Regulations 2011 – HST trailer cars - 2020 accessibility deadline - Porterbrook}}</ref><ref>{{Cite web|url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/855328/emr-lner-angel-hst-dispensation_letter.pdf|title=The Railways (Interoperability) Regulations 2011 – HST trailer cars - 2020 accessibility deadline - Angel Trains}}</ref>{{Update inline|date=July 2023}}

==Australian variant==
[[File:XPT bound for Melbourne at Gunning, New South Wales, 28 March 2009.jpg|thumb|The Australian [[New South Wales XPT|XPT]] variant was built with a larger body and bogies suited to the less stable track found in New South Wales]]

{{main|New South Wales XPT}}

The InterCity 125 was the design basis of the [[New South Wales]] [[New South Wales XPT|XPT]], in cooperation with British Rail. 19 power cars and 60 carriages went into service starting in 1982.<ref>"NSW gives country passengers a break" ''[[Railway Gazette International]]'' March 1979 page 210</ref><ref>"HST begets XPT" ''Railway Gazette International'' June 1980 pages 511–512</ref><ref name="Railmotors&XPTs">{{Cite book |title=Railmotors and XPTs |last1=Cooke |first1=David |publisher=Australian Railway Historical Society (NSW Division) |year=1984 |isbn=0-909650-23-3}}</ref>{{Page needed|date=July 2023}}<ref>{{Cite book |title=HST Silver Jubilee |last1=Marsden |first1=Colin |publisher=Ian Allan Publishing |year=2001 |isbn=0-711028-47-8}}</ref><ref>"XPT Australia's train of tomorrow" ''[[Rail (magazine)|Rail]]'' September 1982 pages 40-42</ref> The XPT is higher and wider than the InterCity 125. The passenger cars were based on a [[Budd Company|Budd]] design, the power cars were shorter, and the engine was downrated and the gearing lowered for a top operating speed of {{convert|160|km/h|mph|abbr=on|round=5}}. The suspension was modified to operate on less stable track, and the cooling system and air filters adapted for the hotter, dustier Australian conditions.<ref>{{Cite news |url=https://trove.nla.gov.au/newspaper/article/125640734 |title=To find out what the XPT can do |date=13 June 1981 |work=The Canberra Times |access-date=13 August 2023 |archive-date=15 May 2018 |archive-url=https://web.archive.org/web/20180515185218/https://trove.nla.gov.au/newspaper/article/125640734 |url-status=live}}</ref> Just as they had in Britain, the trains revolutionised passenger rail schedules and standards.

==See also==
* [[Blue Pullmans]]
* [[Train categories in Europe]]
* [[List of high-speed trains]]
* [[Inter-city rail in the United Kingdom]]
* [[High-speed rail in the United Kingdom]]

== Notes and references ==
{{Reflist|30em}}

== Further reading ==
{{refbegin|30em}}
*{{cite journal |last1=Stanier |first1=W. M. |title=High Speed Train |journal=Railway Engineering Journal |date=1973 |volume=2 |issue=4 |publisher=the Institution of Mechanical Engineers |location=London |issn=0048-6515 |oclc=1559754}}
*{{cite journal |last1=Sephton |first1=B. G. |title=The High Speed Train |journal=Railway Engineering Journal |date=1974 |volume=3 |issue=5 |pages=22–30 |publisher=the Institution of Mechanical Engineers |location=London |issn=0048-6515 |oclc=1559754}}
*{{cite journal |last1=Power |first1=S. R. D. |title=High Speed Train – Fleet Operation |journal=Proceedings of the Institution of Mechanical Engineers |date=1978 |volume=192 |issue=1 |pages=409–419 |doi=10.1243/PIME_PROC_1978_192_042_02 |issn=0020-3483 |s2cid=109968836|doi-access=free }}
*{{cite book
|author=(([[125 Group]]))
|title=Inter-City 125 Owners' Workshop Manual
|year=2019
|publisher=Haynes
|isbn=978-1-78521-266-6}}
*{{cite book
|author=((125 Group))
|title=125 The Enduring Icon
|year=2018
|publisher=Amberley
|isbn=978-1-4456-7859-7}}
*{{cite book
|last=Green
|first=Chris
|title=The InterCity Story 1964–2012
|year=2013
|publisher=OPC
|isbn=978-0-86093-652-7}}
*{{cite book
|last=Jane's Information Group
|title=Jane's World Railways
|year=1978
|publisher=Jane's Information Group}}
*{{cite book
|last=Roza
|first=Greg
|title=The Incredible Story of Trains
|year=2004
|publisher=Rosen Publishing
|isbn=0-8239-6712-3
|url-access=registration
|url=https://archive.org/details/incrediblestoryo0000roza
}}
*{{cite book
|last=Sievert
|first=Terri
|title=The World's Fastest Trains
|year=2002
|publisher=Ian Allan
|isbn=0-7368-1061-7}}
*{{Solomon-Masterpieces}}
*{{cite book|url=http://www.barrowmoremrg.co.uk/BRBDocuments/CS/Book_No_230_EK_web.pdf|title=Vehicle Diagram Book No. 230 for Diesel Electric Multiple Unit Trains (including H.S.T.)|author=Barrowmore MRG|publisher=British Railways Board|date=September 1987|at=GH102-3, GH202-3, GJ201, GK101-2, GK202, GK401, GL101, GL402, GM401, GN401}}
*{{cite magazine|title=Have a banana!|first=Chris|last=Kapolka|magazine=[[Rail (magazine)|Rail Enthusiast]]|publisher=EMAP National Publications|date=February–March 1982|pages=58–59|issn=0262-561X|oclc=49957965}}
*{{cite magazine|title=The ABC of the HST|first=Basil|last=Cooper|magazine=[[Rail (magazine)|Rail Enthusiast]]|publisher=EMAP National Publications|date=June 1982|pages=28–33|issn=0262-561X|oclc=49957965}}
*{{cite magazine|title=Keep the HSTs flying|first=Peter|last=Kelly|magazine=[[Rail (magazine)|Rail Enthusiast]]|publisher=EMAP National Publications|date=May 1983|pages=39–42|issn=0262-561X|oclc=49957965}}
{{refend}}

== External links ==
{{commons category}}
{{commons}}
* [https://web.archive.org/web/20090202134053/http://www.h2.dion.ne.jp/~dajf/byunbyun/speeds/records.htm World speed records]
* [http://www.125Group.org.uk 125 Group]
* [http://www.brushtraction.com Brush Traction]
* [https://web.archive.org/web/20090915204316/http://www.traintesting.com/HST_prototype.htm Testing the prototype HST]
*[https://player.bfi.org.uk/free/film/watch-overture-one-two-five-1978-online ''Overture One-Two-Five'' (1978), British Film Institute]

{{British Rail Locomotives}}
{{High-speed rail}}

[[Category:High-speed trains of the United Kingdom]]
[[Category:Railway services introduced in 1976]]
[[Category:Passenger trains running at least at 200 km/h in commercial operations]]
[[Category:Rolling stock innovations]]
[[Category:United Kingdom streamliner trains]]
[[Category:Diesel multiple units with locomotive-like power cars]]