View source for British Rail Class 37

{{Short description|Class of diesel–electric locomotives}}
{{More citations needed|date=June 2019}}
{{Use British English|date=February 2015}}
{{Use dmy dates|date=June 2025}}
{{Infobox locomotive
| name = English Electric Type 3<br/>British Rail Class 37
| powertype = Diesel–electric
| image = File:5191693456 59e928f289 Steve Jones.jpg
| caption = A Class 37/0 at Aviemore in August 1978
| builder = [[English Electric]] at [[Vulcan Foundry]] and [[Robert Stephenson and Hawthorns]]
| serialnumber = 
| builddate = 1960–1965
| totalproduction = 309 <!-- please do NOT alter this to 308: D6700–6999 is 300, plus D6600–8 (9) makes 309; but D6983 was withdrawn October 1966 after less than 2 yrs service which is why lists dated 1967 or later show 308 -->
| gauge = {{RailGauge|ussg|allk=on}}
| primemover = {{ubl|''Built:'' [[English Electric diesel engines|English Electric 12CSVT]]|''37/9:'' [[Blackstone & Co|Mirrlees Blackstone]] MB275Tt or [[Ruston & Hornsby|Ruston]] RK270Tt}}
| enginetype = V12 Diesel Engine
| aspiration = [[Turbocharger]]
| alternator = Main: Brush BA10005A (37/4, 37/5, 37/6, 37/7 and 37/9) or GEC G564AZ (37/7)[3]Aux: Brush BA606A (37/4, 37/5, 37/6, 37/7 and 37/9)[3] ETS: Brush BAH701 (37/4)[3]
| generator = {{ubl|Original:|Main: English Electric EE822, Aux EE911/5C|Rebuilt locos:|Main: Brush BA1005A alternator, Aux: Brush BA606A<ref name="rc37"/>}}
| tractionmotors = [[English Electric]] [[Direct current|DC]] traction motors<ref name="rc37"/>
| cylindersize = {{cvt|10|×|12|in|mm}} (bore × stroke)
| transmission = [[Diesel electric]]
| Britishclass = [[Co-Co locomotives|Co-Co]]
| uicclass = Co′Co′
| wheeldiameter = {{convert|3|ft|9|in|m|3|abbr=on}}
| minimumcurve = {{convert|4|chain|m|lk=in}}
| locobrakes = [[Vacuum brake|Vacuum]], [[Railway air brake|Air]], [[Vacuum brake#Dual brakes|Dual]]
| trainbrakes = [[Vacuum brake|Vacuum]], [[Vacuum brake#Dual brakes|Dual]], or [[Railway air brake|Air]]
| locobrakeforce = {{convert|50|LTf|kN|sigfig=3|abbr=on|lk=in}}
| wheelbase = {{convert|50|ft|8|in|m|2|abbr=on}}
| length = {{convert|61|ft|6|in|m|2|abbr=on}}
| width = {{convert|8|ft|10+1/2|in|m|2|abbr=on}}
| height = {{convert|12|ft|9|in|m|2|abbr=on}}
| locoweight = {{convert|100|LT|t ST|sigfig=3}} to {{convert|105|LT|t ST|sigfig=3}}<br/>except 37/7 and 37/9 class – ballasted to {{convert|120|LT|t ST|sigfig=3}}<ref name="rc37"/>
| safety = [[Automatic warning system|AWS]]
| maxspeed = {{convert|90|mph|abbr=on}} or {{convert|80|mph|abbr=on}} with regeared CP7 bogies.
| poweroutput = ''Engine:'' {{convert|1750|bhp|0|abbr=on}}
| tractiveeffort = {{ubl|''Maximum:'' {{convert|55500|lbf|kN|0|abbr=on}}|''Continuous:'' {{convert|35000|lbf|kN|0|abbr=on}} @{{convert|13.6|mph|km/h|0|abbr=on}}}}
| fueltype = [[Diesel fuel|Diesel]]
| fuelcap = {{convert|890|impgal|abbr=on}} increased to {{convert|1690|impgal|abbr=on}} on rebuild<ref name="rc37"/>
| lubecap = {{cvt|120|impgal|l}}
| watercap = {{cvt|160|impgal|l}}
| trainheating = {{ubl|''37/0:'' [[Steam generator (railroad)|Steam]]|''37/4:'' [[Head end power|Electric Train Heat]]|''Remainder:'' None}}
| multipleworking = <span style="color:blue;">★</span> Blue Star
| axleloadclass = [[Route availability]] 5<br />except subclass 37/7 RA 7
| operator = {{ubl|[[British Rail]]|[[Colas Rail]]|[[DB Cargo UK|EWS]]|[[Direct Rail Services]]|[[West Coast Railways]]|[[Europhoenix]]|[[Rail Operations Group]]|[[Locomotive Services Limited]]}}
| fleetnumbers = D6700–D6999, D6600–D6608; later 37001–37308
| nicknames = Tractor, also Syphon, Growler or Slugs<ref name="tractor"/>
| withdrawndate = 1967–present
| disposition = 35 preserved, 66 still in service, 1 rebuilt as Class 23, remainder scrapped
| aarwheels = C-C
}}

The '''British Rail Class 37''' is a [[Diesel locomotive|diesel–electric locomotive]].  Also known as the '''English Electric Type 3''', the class was ordered as part of the [[British Rail Modernisation Plan|British Rail modernisation plan]]. They were numbered in two series, D6600–D6608 and D6700–D6999.<ref>{{cite web |url=http://www.brdatabase.info/locoqry.php?action=class&type=D&id=32  |title=37 Co-Co |website=BRDatabase}}</ref>

Built in the early 1960s, the Class 37 became a familiar sight on many parts of the [[British Rail]] network, in particular forming the main motive power for [[InterCity (British Rail)|InterCity]] services in [[East Anglia]] and within [[Scotland]]. They also performed well on secondary and inter-regional services for many years. Many are still in use today on freight, maintenance, and empty stock movement duties. The Class 37s are known to some railway enthusiasts as "[[tractor]]s",<ref name="tractor">{{cite web |url=http://www.rodge.force9.co.uk/faq/nicknames.html |title=Locomotive, DMU and EMU Nicknames |publisher=Rodge.force9.co.uk |access-date=25 March 2014 |url-status=dead |archive-url=https://web.archive.org/web/20100130050342/http://www.rodge.force9.co.uk/faq/nicknames.html |archive-date=30 January 2010}}</ref> a [[nickname]] given due to the similarities between the sound of the Class 37's engine and that of a tractor.

== Description ==

=== Background ===
As part of the large scale [[dieselisation]] brought about by the [[History of rail transport in Great Britain 1948 - 1994#The Modernisation Plan|British Rail modernisation plan]] a need was identified for a number of [[British Rail locomotive and multiple unit numbering and classification#1957 numbering and classification|type 3 locomotives]] with a power output of {{convert|1500|hp|abbr=on}} to {{convert|1999|hp|abbr=on}}. English Electric had already been successful with orders for [[British Rail Class 20|type 1]] and [[British Rail Class 40|type 4]] diesels, and had produced locomotives of similar power for railways in East Africa. A design based on the exported locomotives was put forward and accepted.<ref>{{cite web|url=http://www.kentrail.org.uk/Class%2037.htm |title=Class 37 English Electric Type 3 : kentrail.co.uk (Background to original order) |publisher=Kent Rail |access-date=25 March 2014}}</ref> The design was for a general purpose locomotive and initially found service in British Rail's Eastern Region.<ref>{{Cite web |url=http://www.modern-locoillustrated.com/MLI%20issue%20downloads/Issue%20171/EE_type_3_booklet.pdf |archiveurl=https://web.archive.org/web/20100704234500/http://www.modern-locoillustrated.com/MLI%20issue%20downloads/Issue%20171/EE_type_3_booklet.pdf |url-status=dead |title=1,750 H.P. Diesel-Electric Locomotives |date=15 November 2023 |archivedate=4 July 2010}}</ref>

=== Building ===
[[File:BR Class 37 D6712.jpg|thumb|left|D6712 in BR green livery departing Ely in 1971]]
There was no prototype. British Railways placed an order for forty-two Class 37 locomotives in January 1959.<ref>{{harvnb|Clough|2009|p=86}}</ref> The first was delivered in November 1960; it entered service on 2 December.<ref>{{harvnb|Clough|2009|p=87}}</ref> BR had ordered further Class 37s before the last of the original batch had been completed in mid-1962. The final locomotive was delivered to the [[Western Region of British Railways|Western Region]] on 9 November 1965.<ref>{{harvnb|Clough|2009|p=88}}</ref> [[English Electric]] split the construction between [[Vulcan Foundry]] at [[Newton-le-Willows]], and [[Robert Stephenson and Hawthorns]] of [[Darlington]].<ref name="rc37">{{cite web |url=http://www.therailwaycentre.com/New%20Loco%20Tech%20Data/Class37.html |title=Class 37 |publisher=The Railway Centre |access-date=25 March 2014 |archive-url=https://web.archive.org/web/20130926045130/http://www.therailwaycentre.com/New%20Loco%20Tech%20Data/Class37.html |archive-date=26 September 2013 |url-status=usurped}}</ref> The 309 locomotives produced in total were originally numbered in the range D6700–D6999 and D6600–D6608. The bodywork bears a strong family resemblance to other English Electric designs such as the {{brc|40}} and {{brc|23|Baby Deltic}}. Vehicles from D6819 onwards were built without nose-end doors and the [[headcode]] display was changed from a split pair of boxes to a panel on the centre of the nose.<ref>{{cite magazine |title=English Electric's Go Anywhere Type 3 |first=Evan |last=Green-Hughes |magazine=Hornby Magazine |pages=74–77 |issue=46 |date=April 2011 |location=Hersham |publisher=Ian Allan Publishing |issn=1753-2469 |oclc=226087101}}</ref>

Seven orders were placed with English Electric, as follows:<ref>{{harvnb|Clough|2009|pp=86–88}}</ref>
{|class=wikitable style="clear:left;"
|-
!EE order no. !!Date !!Total !!Numbers !!Works
|-
|CCL 1031 ||27 January 1959 ||42 ||D6700–41 ||[[Vulcan Foundry]]
|-
|rowspan=2|CCM 1114 ||rowspan=2|5 February 1960 ||rowspan=2|37 ||D6742–68 ||Vulcan Foundry
|-
|D6769–78 ||[[Robert Stephenson and Hawthorns]]
|-
|CCN 1239 ||27 April 1961 ||17 ||D6779–95 ||Robert Stephenson and Hawthorns
|-
|CCP 1267 ||13 December 1961 ||23 ||D6796–6818 ||Vulcan Foundry
|-
|rowspan=2|CCP 1304 ||rowspan=2|July 1962 ||rowspan=2|100 ||D6819–28, D6859–68, D6879–98 ||Robert Stephenson and Hawthorns
|-
|D6829–58, D6869–78, D6899–6918 ||Vulcan Foundry
|-
|CCR 1320 ||January 1964 ||20 ||D6919–38 ||Vulcan Foundry
|-
|CCS 1362 ||February 1964 ||70 ||D6939–99, D6600–8 ||Vulcan Foundry
|}

=== Duties ===
{| class="floatright wikitable"
|+Distribution of locomotives,<br/>March 1974<ref>{{cite book |title=British Railways Locoshed Book 1974 edition |year=1974 |publisher=[[Ian Allan Publishing|Ian Allan]] |location=Shepperton |isbn=0-7110-0558-3 |pages=25–28}}</ref>
|-
|colspan=3 |{{Location map+ |England|width=220 |caption= |places=
 {{Location map~|England|lat_deg=51.4761 |lon_deg=-3.1940 |label=CF |link=Cardiff Canton TMD |marksize=16 }}
 {{Location map~|England|lat_deg=55.8911 |lon_deg=-4.2403 |label=ED |link=Eastfield TMD |marksize=12 |position=bottom }}
 {{Location map~|England|lat_deg=54.9637 |lon_deg=-1.6104 |label=GD |link=Gateshead TMD |marksize=14 }}
 {{Location map~|England|lat_deg=53.6647 |lon_deg=-1.5826 |label=HM |link=Healey Mills TMD |marksize=9 |position=top }}
 {{Location map~|England|lat_deg=53.619 |lon_deg=-0.1894 |label=IM |link=Immingham engine shed |marksize=11 }}
 {{Location map~|England|lat_deg=51.6398 |lon_deg=-3.9402 |label=LE |link=Landore TMD |marksize=16 |position=top }}
 {{Location map~|England|lat_deg=52.565 |lon_deg=0.0824 |label=MR |link=March TMD |marksize=14 }}
 {{Location map~|England|lat_deg=51.5455 |lon_deg=-0.0060 |label=SF |link=Stratford TMD |marksize=13 }}
 {{Location map~|England|lat_deg=54.5598 |lon_deg=-1.2893 |label=TE |link=Thornaby TMD |marksize=16 }}
 {{Location map~|England|lat_deg=53.3956 |lon_deg=-1.3765 |label=TI |link=Tinsley Motive Power Depot |marksize=14 |position=bottom }}
}}
|-
!Code ||Name ||Quantity
|-
|style="text-align:center" |CF ||[[Cardiff Canton TMD|Cardiff Canton]] ||style="text-align:right" |51
|-
|style="text-align:center" |ED ||[[Eastfield TMD|Eastfield]] ||style="text-align:right" |19
|-
|style="text-align:center" |GD ||[[Gateshead TMD|Gateshead]] ||style="text-align:right" |28
|-
|style="text-align:center" |HM ||[[Healey Mills TMD|Healey Mills]] ||style="text-align:right" |9
|-
|style="text-align:center" |IM ||[[Immingham engine shed|Immingham]] ||style="text-align:right" |16
|-
|style="text-align:center" |LE ||[[Landore TMD|Landore]] ||style="text-align:right" |47
|-
|style="text-align:center" |MR ||[[March TMD|March]] ||style="text-align:right" |29
|-
|style="text-align:center" |SF ||[[Stratford TMD|Stratford]] ||style="text-align:right" |27
|-
|style="text-align:center" |TE ||[[Thornaby TMD|Thornaby]] ||style="text-align:right" |50
|-
|style="text-align:center" |TI ||[[Tinsley Motive Power Depot|Tinsley]] ||style="text-align:right" |32
|-
|colspan=2 |Withdrawn (1966) ||style="text-align:right" |1
|-
!colspan=2 scope=row |Total built:
|style="text-align:right" |309
|}
The class was designed for freight work and to haul passenger trains on secondary routes and as such the gearing was kept low.{{sfn|Morrison|1981|p=4}} Many of the original locomotives were fitted with [[Steam generator (railroad)|boilers for steam heating]]. D6700–6754 were fitted with boilers from new, along with D6758, D6775, D6781–D6818, D6875–D6892. D6960–6968 received boilers from D6701–6709 during 1967/68. 37247 was fitted with a boiler in 1977. With the withdrawal of many Type 2 and Type 3 locomotives in the 1980s the 37s were selected as the standard Type 3 and many of the fleet were given a heavy overhaul to prolong their life into the 1990s and beyond. Some were fitted with [[Head end power|electrical train heating]] (ETH) equipment in the 1980s to become the 37/4 sub-class, initially for use on the [[West Highland Line]], the [[Welsh Marches line]] and South Wales–Bristol area services and [[Far North Line]]s but later seeing use in north/mid Wales and occasionally the West Country. In 2010, they were used on passenger services on the [[Cumbrian Coast Line]] and [[Wherry lines]].

=== High speed trial ===
In 1965 the [[Western Region of British Railways|Western Region]] undertook some trials using a pair of Class 37s to operate express passenger trains at up to {{convert|100|mph|kph}}. These were successful enough for some such running to continue and diagrams using this combination operated between {{stn|Paddington}} and {{stn|Bristol Temple Meads}} until 1967. However it was found that there was excessive wear due to constant high-speed running and this resulted in the cessation of these turns.{{sfn|Morrison|1981|p=18}}

=== Rebuilding ===
A number of locomotives were rebuilt as Class 37/9s in the late 1980s to evaluate [[Blackstone & Co|Mirrlees]] and [[Ruston & Hornsby|Ruston]] engines for possible use on a new [[List of British Rail unbuilt locomotive classes#Type 3 locomotives|Class 38]] freight locomotive. These locos were heavily ballasted to improve traction and had excellent load-hauling capabilities, but the Class 38, understood to be a 'modular' locomotive based on the approach that gave rise to the {{brc|58}} diesel loco and the proposed [[List of British Rail unbuilt locomotive classes#Electric locomotives|Class 88]] electric loco, was never built.

=== Axle load ===
[[File:Class 37 cab.jpg|right|thumb|Cab interior of loco no. 37052]]
The Class 37 has a relatively low axle loading for its size and power. With the withdrawal of most of the smaller types of diesel locomotive, this left it as the only mainline type available in significant numbers for lines with weight restrictions, and for a number of years 37s handled almost all locomotive-hauled services on the West Highland Line, the lines north of [[Inverness railway station|Inverness]] (the [[Far North Line|Far North]] and [[Kyle of Lochalsh line|Kyle]] lines) and in parts of [[Wales]]. The Class 37 has [[Route Availability]] 5 and this is one of the main reasons it is still in use on the network.  Note that class 37/7 and 37/9 have an RA of 7 due to their extra ballast weights.

=== Regional variations ===
There are several differences between particular locomotives, some of them easily seen. Western Region Class 37s can be identified by 'cow horns' around halfway up on the outer edge of each end of the lamp brackets. When British Railways took over from the [[Great Western Railway]] the use of Great Western lamps continued. Their brackets used an L-shaped upright that was parallel to the direction of travel, unlike the other regions which used transverse brackets.{{citation needed|date=April 2023}}

From the late 1970s some Western Region Class 37s were fitted with additional brackets on the nose to mount an additional headlight for use on the [[Heart of Wales line]].{{sfn|Morrison|1981|p=104}}

Another difference between the regions is by the nose end headcodes. Lower-numbered, split-box Class 37s were allocated to northern England and east Anglia; centre-box locomotives were almost all allocated to Wales and the south west. After locomotives were transferred between pools in the 1980s they tended to stray from their original depots.

Regional decorations included the Highland ([[Inverness TMD|Inverness]]) Stag, the Cockney Sparrow ([[Stratford TMD|Stratford]]) the Cornish lizard ([[St Blazey engine shed|St Blazey]]) and [[Eastfield TMD|Eastfield]] Highland Terrier. All the [[Cardiff Canton TMD|Cardiff Canton]] Class 37/4s received Celtic Dragons below the driver's window whilst in large logo blue. Some Scottish locomotives were later fitted with small Saltire flags by their TOPS data panels or on their noses in a similar fashion to the HAA hoppers allocated to Scottish power stations.

=== British Rail liveries ===
On delivery, the Class 37s were painted in plain green with a grey roof, the 'late' (post-1956) British Railways crest and a D prefix to their running number. Some locomotives were delivered as the small yellow warning panel was introduced, earlier locomotives being given these panels during works visits. Towards the late 1960s, the yellow was extended to the full height of the nose.

[[File:37057 Viking.jpg|thumb|left|37057 ''Viking'' in BR 'Large Logo' blue livery at Eastleigh, 1992]]
By the 1970s, all locomotives had received all over British Rail blue with a full yellow nose; by 1975 most locomotives had also received their [[TOPS]] numbers. Their livery remained the same until the early 1980s when 'Large Logo blue' was introduced. This entailed the yellow nose continuing round to behind the driver's door and up to the top of the windscreen and a full height 'double arrow' logo. These locomotives had the top of the nose painted black to lower the risk of the driver being dazzled by the sun. Freight-allocated examples received a similar livery{{snd}}the only difference being the blue was replaced by freight grey. In 1987, the Sectors were launched, incorporating a new livery of 'three tone grey'; a light grey lower bodyside, medium grey cantrail and a dark grey roof, along with a bright Sector logo (Coal, Metals, Petroleum, Distribution, General and Construction). In addition a metal double arrow logo was fitted. This livery co-existed with plain blue, large logo blue/grey and the new [[InterCity (British Rail)|InterCity]] and [[Regional Railways]] liveries right up to the end of British Rail in 1996.

[[File:37891 British Rail class 37 diesel loco.jpg|thumb|37891 with [[Mainline Freight]] branding at Eastleigh, 1995]]
Some locomotives in the 'sectorised company' pools received [[Transrail Freight]] logos or [[Mainline Freight]] 'Rolling Balls' over their triple grey colours, while [[Loadhaul]] locomotives were painted orange and black and Mainline locomotives received 'aircraft' blue with silver stripes. Departmental locomotives were initially painted in a plain grey livery, but this didn't find favour and was modified into 'Dutch' grey and yellow livery, similar to that of [[Nederlandse Spoorwegen]]. Locomotive 37093 was mocked up as a "police" locomotive which pulled over a [[British Rail Class 43 (HST)|Class 43 HST power car]] for speeding in an [[InterCity 125]] advert broadcast in the 1980s.<ref>{{cite web |title=British Railways Advert – HST v Class 37 Police Car!! | website=[[YouTube]] | date=9 January 2008 |url=https://www.youtube.com/watch?v=iN7naLLeB0A |access-date=27 August 2023}}</ref>

== TOPS renumbering ==
{{Main|List of British Rail Class 37 locomotives}}
As with many diesel classes, the [[TOPS]] renumbering was implemented in a straightforward manner, with the locomotive numbers remaining in sequence; thus D6701 became 37001, D6999 became 37299 and D6600–D6608 became 37300–37308. The remaining locomotive, D6700, became 37119 instead of D6819, which became 37283; the number was unused as D6983 was destroyed in an accident in 1965.{{cn|date=June 2025|reason=[[WP:SPS]] removed}} As members of the class were altered later in their careers, they were renumbered, some more than once.

D6983 was withdrawn in December 1965 following a fatal collision with a derailed {{brc|47}}, D1671 ''THOR'', near [[Bridgend]] in South Wales; this was caused by a landslip. D6983 was the first EE Type 3 to be withdrawn and, as a result, the only locomotive in the entire class not to receive a TOPS number. The remains of both locomotives were sold to local scrap merchants, R.S. Hayes, and cut up the following year.{{sfn|Morrison|1981|p=33}}

== Sub-classes ==
In the 1980s the Class 37 locomotives were extensively refurbished{{spaced ndash}} from that point 37/0 refers to the original version. The work took place at [[British Rail Engineering Limited|British Rail Engineering]]'s [[Crewe Works]] except for the 37/3 subclass whose bogies were replaced at various depots.<ref name="rc37"/>
{| class="wikitable"
!Sub-class
!align=left|Description
|-
|37/0
|Locomotives which remained unmodified after other sub-classes were created
|-
|37/3
|Locomotives which were rebogied but not refurbished
|-
|37/4
|Refurbished, rewired, English Electric generator replaced with Brush alternator, electric train supply (ETS) fitted
|-
|37/5
|Refurbished, rewired, English Electric generator replaced with [[Brush Traction]] alternator
|-
|37/6
|Locomotives from Class 37/5 further modified with through ETS wiring and RCH jumper cables
|-
|37/7
|Refurbished, rewired, English Electric generator replaced with [[General Electric Company|GEC]] G564AZ or Brush alternator,<ref name="rc37"/> additional weight added
|-
|37/9
|Refurbished, rewired, English Electric generator replaced with Brush alternator, new engines: [[Blackstone & Co|Mirrlees]] MB275Tt or [[Ruston & Hornsby|Ruston]] RK270Tt<ref name="rc37"/>
|}

===Class 37/0===
[[File:37 263 at Didcot.jpg|thumb|left|37263 at [[Didcot Parkway railway station|Didcot]]]]
This designation covered all 309 locomotives as built, but with such a large number of locomotives and with two companies involved in the building, there were several differences within this sub-class alone. The most visible external difference was that the first 119 locos (originally) had a "split" headcode box; for these locos the four digit [[train reporting number]] was shown in two square boxes, each containing two digits and separated by a pair of connecting doors, designed to allow the train crew to be exchanged while in motion. Later locomotives had a single centrally placed headcode box and also had the horns mounted on the roof, rather than built into the nose of the locomotive. This difference was the reason for the double change in numbers (involving D6700 and D6819) when implementing the [[TOPS]] scheme described earlier.

From the mid-1970s onwards some locomotives that had been built with steam heating boilers and where these were not longer used had the associated water tank converted for use as an additional fuel tank, extending the fuel capacity to {{convert|1750|impgal|L}}.{{sfn|Morrison|1981|p=34}}

===Class 37/3===
[[File:37 371 at Eastleigh.jpg|thumb|37371 at [[Eastleigh railway station|Eastleigh]]]]
There were two incarnations of a 37/3 subclass. The first was a group of 12 [[Motherwell TMD|Motherwell]] allocated locos that were fitted with strengthened couplings and modified brake blocks for working the heavy trains to [[Ravenscraig]]. These were all renumbered back to their original numbers by the end of 1988.{{citation needed|date=April 2023}} Starting in 1979 triple-heading on iron ore hoppers between Port Talbot and Llanwern in South Wales commenced, typically using locomotives in the range 37 299-37 308.{{sfn|Morrison|1981|p=101}}

The second set of locos were rebogied at various depots with the regeared cast frame type 'CP7 Bogie'. Bogies from the English Electric {{brc|55|Deltics}}, {{brc|50}} and Class 37s are largely interchangeable with only modification to traction motor gearing, to {{convert|80|mph}} in the case of the 37s, and access step positions needing alteration between the classes. The fuel capacity was doubled by using the redundant train heating boiler water tanks but no other changes were made.{{cn|date=June 2025|reason=[[WP:SPS]] removed}}

===Class 37/4===
[[File:BR Class 37 37 409.jpg|thumb|left|BR Class 37/4 37409 ''Loch Awe'' at {{rws|Fort William}} in 1989]]
With ETH ([[Electric Train Heating]]) replacing 'steam heated' coaches, some of this class received ETH Supply when refurbished at [[Crewe Works]] during 1985 and 1986. During this refurbishment, the locomotives also received regeared CP7 [[bogies]] and the English electric generator was replaced with a [[Brush Traction|Brush]] BA1005A [[alternator]].<ref>{{cite web |url=http://www.railfaneurope.net/pix/picmonth/1997-12.html |title=The European Railway Picture Gallery Class 37/4 data sheet |publisher=Railfaneurope.net |date=13 May 1965 |access-date=25 March 2014 |archive-date=24 September 2015 |archive-url=https://web.archive.org/web/20150924111154/http://www.railfaneurope.net/pix/picmonth/1997-12.html |url-status=dead}}</ref> Extensive re-wiring, as well as a full repaint into [[British Rail corporate liveries#Moving away from Rail Blue|BR Large Logo]] was undertaken. The modifications allowed the rebuilt locomotives to work passenger trains all year round, with the 31 strong fleet being split between [[Wales]] and [[Scotland]], Scotland receiving the first 25 and Wales the other six.

After the extensive refurbishment, the locomotives were allocated the 37/4 sub-class, following the trend of renumbering 'ETH' fitted locomotives xx/4s, (e.g. 474xx and 314xx).

The next chapter saw the entire sub-class pass to [[Transrail Freight]], which was one of the three regional [[Freight operating company|freight operating companies]] prior to the privatisation of the entire British Rail network.

Over the years, the locomotives have received a large number of liveries: BR Green, [[Regional Railways#Livery|Regional Railways]], Trainload Grey, [[DB Cargo UK|EWS]] maroon, [[Transrail Freight]], BR Large Logo and Mainline, to name a few.

The [[Cambrian Line|Cambrian]], [[North Wales Coast Line|North Wales Coast]], [[Rhymney line|Rhymney]], [[West Highland Line|West Highland]], [[South Wales Main Line|South Wales]] and [[West of England Main Line|West Country]] all benefited from the use of 37/4s.

Locomotive hauled operations had virtually ceased by the early 2000s, thanks to the widespread introduction of second-generation diesel multiple units and the replacement of loco hauled trains by multiple units, although the sub-class did hold out on the [[Rhymney line|Cardiff–Rhymney]] trains for [[Arriva Trains Wales]] for some years. 37411 and 37425 were specially painted to mark the end of loco-hauled services on the line, in April 2005, these repaints being funded by Arriva.

In late 2010 [[DB Cargo UK|DB Schenker]] put all of its remaining 37/4s up for sale, with many examples expected to be sold for scrap. [[Direct Rail Services]] (DRS) subsequently bought most of the remaining class 37/4s,<ref>Rail Express April 2011 {{full citation needed|date=January 2025}}</ref> for use on nuclear flask traffic. These later found further use in 2018/19 on Cumbrian Coast passenger services and East Anglian passenger services between Norwich and Great Yarmouth/Lowestoft, allowing for multiple units to be cascaded (in the first instance) and covering for accident damaged units (in the second). Between 2019 and early 2020 [[Colas Rail]] hired three Class 37s, including 37418 and 37421, to [[Transport for Wales]] for use (once again) on peak hour commuter services on the Rhymney line.

===Class 37/5===
[[File:37 667 BR diesel locomotive.jpg|thumb|Class 37/5 number 37667 at Eastleigh]]
This class were updated in similar fashion to the 37/4 subclass, except that they did not receive electric train heating and some were fitted with Sandite ports. Locomotives previously numbered between 37001 and 37119 (those which had split headcode boxes) were given new numbers from 37501 upwards (curtailed at 37521); those previously numbered between 37120 and 37308 were renumbered from 37699 downwards (curtailed at 37667). Nine locomotives from the first batch and three from the second were later modified for use with the aborted Channel Tunnel sleeper Nightstar project, reclassified 37/6 and renumbered 37601–37612 (see below).

===Class 37/6===
[[File:37603 and 37604 At Clapham Junction.jpg|thumb|left|Two [[Eurostar]] 37/6 types at {{rws|Clapham Junction}}]]
[[Eurostar]] (at the time European Passenger Services) had 12 locomotives modified (all ex-37/5) as Class 37/6, with the intention that they would haul overnight international trains ("[[Nightstar (train)|Nightstar]]") over the non-electrified sections of their routes in Britain. However, these services were never introduced, and, in 1997, Eurostar sold six of its locomotives to [[Direct Rail Services]] (DRS), with a further three sold in 2000. The remaining three locomotives were retained by Eurostar for a variety of tasks, including driver training, route learning, and for rescuing failed {{brc|373}} units. Once Eurostar moved its operations to its new depot at [[Temple Mills TMD|Temple Mills]], its Class 37 locomotives became redundant and they too were sold to DRS in 2007.  DRS has subsequently sold some of them, [[Europhoenix]] being the principal recipient.  The Europhoenix 37/6s are used on test trains and have been used to haul EMUs to and from works and to rail-connected scrapyards.{{citation needed|date=April 2021}}

===Class 37/7===
[[File:37710 stabled at Didcot Yard.JPG|thumb| [[Loadhaul]] liveried 37/7 type]]
The Class 37/7 sub-class was intended primarily for heavy freight work, with extra ballast and modified gearing.

As part of the major refurbishment scheme of the Class 37 locomotives in the 1980s, another freight dedicated fleet of 44 Class 37s was created, the Class 37/7 subclass, which was very similar to the 37/5 subclass except for plating over of a bodyside window and the addition of a ballast weight to give extra 'pulling power' when hauling heavy freight trains, such as the metals trains in South Wales. Again, like the 37/5s, there were two batches completed; from phase 1 and phase 2 Class 37/0 locos. The batch numbered 37701 upwards (curtailed at 37719) were from phase 1 build locos and have the flush front ends and nose-mounted horns, whilst the batch numbered from 37899 downwards (curtailed at 37 883) were rebuilds from phase 2 locos, having the central headcode box (plated over) and roof-mounted horns. A further batch was created; locos numbered 37796–37803 had a different type of electrical equipment fitted (from Brush), as part of a trial, and differ from the other locos in the subclass internally.

In British Rail use the sub-class were particularly common in South Wales on heavy coal and metals work. They were particularly adept at working coal trains up and down the short but steeply graded branch lines around Swansea and Cardiff, to collieries such as Tower Colliery, Coedbach and Cwmbargoed. They operated [[merry-go-round train]]s of 32-ton HAA air-braked hoppers, usually numbering 32 wagons, between collieries, washeries, open cast mines and disposal points to power stations such as Aberthaw and occasionally further afield.

Their use on Metals Sector trains, usually from Llanwern, Port Talbot or English metal works such as Scunthorpe, saw them hauling very heavy trains between docks, works and purchasers in Britain. Indeed, the use of three Class 37/0 locomotives on Llanwern–Port Talbot Docks steel trains (the heaviest on the British rail network at {{convert|3300|LT}} was soon abandoned when Class 56s became available, requiring only two locomotives. Cardiff had a large allocation of 37/7s, some waiting on standby, ready for a call from the mills requiring more wagons to handle any extra traffic. Eventually this work was taken over by {{brc|56|s}} and {{brc|60|s}}. This Metals traffic would also become the domain of the sub-class 37/9, which to all intents and purposes was a 37/7 but with a different [[prime mover (locomotive)|prime mover]].

When [[DB Cargo UK|EWS]] introduced its 250 {{brc|66|s}}, from 1998, many of the sub-class were put into store. Some have since been involved in construction work in France  and Spain building new high-speed lines. A total of 40 were sent to France, 15 to Spain and an additional two were sent to Italy.<ref name="Platform 5, 118">{{cite book |title=Preserved Locomotives of British Railways |edition=20 |year=2022 |page=118 |isbn=978-1909431980 |last1=Pritchard |first1=Robert N. |last2=Beardsley |first2=Ian |publisher=Platform 5 Publishing Limited }}</ref> Most subsequently returned to the UK, although a handful were broken up abroad.{{cn|date=June 2025}}

=== Class 37/9 ===
[[File:Train at Craven Arms - 1990 - (2) - geograph.org.uk - 4117913.jpg|thumb|37905 hauls a train of steel coils through Craven Arms station]]
In 1986, four Class 37s, numbers 37150/148/249/124 respectively, were converted to test the [[Mirrlees Blackstone|Mirrlees]] MB275T engine<ref name="RE63-55">{{cite magazine |title=Enter the Super 'Syphons' |magazine=[[Rail (magazine)|Rail Enthusiast]] |publisher=EMAP National Publications |date=December 1986 |issue=63 |pages=55–57 |issn=0262-561X |oclc=49957965}}</ref> and [[Brush Traction|Brush]] alternator for the proposed [[List of British Rail unbuilt locomotive classes|Class 38]], and were numbered 37901–904. These were followed in 1987 by 37905/6, converted from 37136/206, which were fitted with the alternative pairing of a [[Ruston & Hornsby|Ruston]] RK270T engine and [[General Electric Company|GEC]] alternator.<ref name="RE63-55"/> All six locomotives were fitted with new bogies, and had ballast weights to increase their overall weight to 120 [[Long ton|tons]]. Although intended as a testbed for the proposed Class 38, the two power units fitted were those considered for the {{brc|60}}, which was eventually delivered with an enlarged version of the Mirrlees MB275T. They all had modifications similar to that of Class 37/7, including new nose grilles, removal of the central bodyside windows and 4 fire extinguisher ports. However, 37901-904 had a heavily modified central roof section, consisting of flat panels rather than the curved sheets of the original. All 6 had a new exhaust port fitted, replacing the two of the original design.

All six Class 37/9s were delivered in Railfreight Grey livery, later receiving 3TG metals sub sector livery, and operated as part of the British Rail Heavy Metals sector, being based in [[South Wales]] and hauling trains normally rostered for the much more powerful {{brc|56}} such as the [[Port Talbot Steelworks]]–Llanwern Iron Ore tipplers.<ref>{{cite magazine |last=Banks |first=Alan |title=Masterclass: BR Class 37/9s |magazine=Model Rail |issue=111 |pages=18–24 |publisher=EMAP active Ltd |location=Peterborough |date=December 2007}}</ref> During the late 1990s, use of the Class 37/9s declined due to availability of the newer and more powerful {{brc|66|s}} and problems maintaining such a small number of non-standard locos, with all six officially designated as being in storage in 1999.

This was not, however, the end of the sub-class. In July 2000, 37906 was designated as part of the EWS heritage fleet but has since been sold into preservation, joining 37901 and 37905. 37902 was sold to [[Direct Rail Services]] in 2003, but was scrapped and cut up in 2005 after a review by DRS. 37904 was cut up at [[CF Booth]]'s in [[Rotherham]] in November 2004 and 37 903 was scrapped at [[Crewe Diesel TMD]] in April 2005. 37901 has since been sold to [[Europhoenix]] and returned to service (complete with its ''Mirrlees Pioneer'' name). 37905 was purchased by [[UK Rail Leasing]] and is presently stored at its Leicester depot. In October 2019, 37906 [[Battlefield Line Railway]] was sold.

==Operations==
{{More citations needed|section|date=April 2023}}

===British Rail===
Initially D6700 – D6702 were allocated to [[Stratford TMD|Stratford shed]] and possibly the first use of a Class 37 on a passenger train was on 6 January 1961 when D6700, which had been hauling a test train, was commandeered at {{stn|Bishop's Stortford}} to take the northbound [[Fenman]] forward after the train engine, a {{brc|31}}, had failed near [[Stanstead Abbotts]] and had been brought into the station by a {{brc|15}}. Initial operation of scheduled passenger services on the Liverpool Street to Cambridge line by Class 37s commenced three days later, with D6700 (again) taking the 5.56pm departure from Liverpool Street.{{sfn|Morrison|1981|p=4}}<ref>{{cite magazine |title=Motive Power Miscellany |magazine=Trains Illustrated |location=Hampton Court |publisher=Ian Allan |date=March 1961 |volume=XIV |issue=150 |page=182}}</ref> Initial batches continued to be delivered to sheds in East Anglia and Class 37s operated express trains out of Liverpool Street to {{stn|Norwich}}, {{stn|Harwich International}} and {{stn|Clacton-on-sea}} as well as on the Cambridge line to {{stn|Cambridge}} and beyond to {{stn|King's Lynn}}. The services on this route and on boat trains to Harwich were to be the exclusive preserve of the class for over 20 years.

[[File:37174, Lickey banker.jpg|thumb|37174 at Bromsgrove, banking a freight train on the Lickey incline in 1991]]
From D6730 on, a batch of locomotives was allocated to Hull Dairycoates and operated a variety of freight and secondary passenger turns and, along with further allocations to Hull, there were also locomotives delivered to [[Gateshead TMD|Gateshead]], [[Thornaby TMD|Thornaby]] and [[Tinsley Motive Power Depot|Tinsley]], with D6742 and D6743 from the latter depot being sent for trials in South Wales in late 1962. This trial was so successful that within 2 years there were over 100 Class 37s allocated to the WR depots at [[Landore TMD|Swansea]], [[Cardiff Canton TMD|Cardiff]] and [[Bristol Bath Road depot|Bristol]] and from 1964 the class took over work [[Bank engine|banking]] on the [[Lickey Incline]] with two pairs of locomotives operating in place of the pairs of [[British Rail Class 35|Hymek diesels]] that had previously fulfilled this role. Their main use was assisting freight trains but the one passenger train that regularly required their assistance was the {{stn|Bristol Temple Meads}} to {{stn|Glasgow Central}} & {{stn|Edinburgh Waverley}} [[Sleeping car|sleeper]].{{sfn|Morrison|1981|p=105}}<ref name=Lund/>

Initially the locomotives allocated to Tinsley depot operated passenger services on the ex-LNER routes, notably the [[Pullman train (UK)|Pullman]] service to {{rws|London King's Cross}} and the Harwich boat trains from {{stn|Liverpool Central}} and {{stn|Manchester Piccadilly}} which at that time operated via the [[Woodhead Tunnel]].{{sfn|Morrison|1981|p=17}} Allocations to Scotland commenced in 1965 with lowland depots receiving an allocation predominantly for freight operations.{{sfn|Morrison|1981|p=4}}

By the late 1970s Class 37s were handling the loco-hauled services west of [[Swansea railway station|Swansea]] to [[Fishguard Harbour railway station|Fishguard Harbour]], [[Milford Haven railway station|Milford Haven]] and {{stn|Carmarthen}} although operations to {{stn|Pembroke Dock}} remained the exclusive preserve of DMUs.<ref name=Lund>{{cite book |last=Lund |first=E |title=to the Last Drop |page=14 |isbn=0-9507063-0-2}}</ref>{{sfn|Morrison|1981|p=95}} and also on the Western Region, in early 1978 [[Laira Traction and Rolling Stock Maintenance Depot|Plymouth Laira]] received 37 142 from [[Landore TMD|Landore]] and 37 267 from Stratford to be used on China Clay traffic in place of double-headed {{brc|25|s}}.{{sfn|Morrison|1981|p=81}} Also around this time and on the other side of the country Class 37 locomotives having the later design of nose with the central headcode box were banned from operating into {{stn|Liverpool Street}} over concerns about the clearance between the overhead catenary and the roof-mounted horns.{{sfn|Morrison|1981|p=45}}

In 1977 some of the steam-heat capable locomotives moved to Scotland and were allocated to [[Eastfield TMD|Eastfield]] to replace {{brc|27|s}} on the [[West Highland Line]] and by 1981 all passenger turns on these lines were in their hands.{{sfn|Morrison|1981|p=109}}<ref>{{cite book |last=Webster |first=Neil |title=Loco-hauled travel 1981–82 |publisher=Platform 5 |location=Sheffield |year=1981 |page= 18 |isbn= 0-906579-17-1}}</ref> Also on the [[Scottish Region of British Railways|Scottish Region]] from summer 1982 Class 37s replaced {{brc|26|s}} on the [[Far North Line|Far North]] line and then [[Kyle of Lochalsh line|Kyle of Lochalsh]] line from that autumn.<ref>{{cite book |last=Webster |first=Neil |title=Loco-hauled travel 1982 |publisher=Platform 5 |location=Sheffield |year=1982 |page=18 |isbn= 0-906579-22-8}}</ref><ref>{{cite book |last=Webster |first=Neil |title=Loco-hauled travel 1982-83 |publisher=Platform 5 |location=Sheffield |year=1982 |page=14 |isbn=0-906579-23-6}}</ref> With the introduction of [[British Railways Mark 2|Mark 2d/e/f]] air-conditioned stock 37/0s were coupled to ETHELs (Electric Train Heating Ex-Locomotive) - essentially {{brc|25|s}} with isolated traction motors that provided [[Head End Power|Electric Train Heating]]. By 1985 there were nine class 37s allocated to [[Inverness TMD|Inverness]] and due to plans to retire coaches that required steam-heating and replace them with more modern stock, in that same year 20 Eastfield allocated locomotives were in works for conversion to the 37/4 subclass.<ref>{{cite book |last=Wood |first=Roger |title=British Rail locoshed book (Summer 1985) |publisher=Ian Allan |location=Shepperton |year=1985 |pages=15–16 |isbn=0-7110-1542-2}}</ref>

Class 37s were subject to several modifications during their time in service. One short-lived experiment involved 37175 receiving CP5 'self-steering bogies' designed to reduce excess wear and noise on the tightly curved West Highland line to {{rws|Fort William}} and {{rws|Mallaig}}. This however, proved too expensive to be practicable. Some [[Inverness TMD|Inverness]] allocated Class 37s received 'car lights'; these were essentially spotlights that made them more visible on the sharply curved Scottish branches, especially to users of level crossings. These were eventually either removed or superseded by the modern 'sealed beam' lights that became compulsory from 1993. Other classes fitted with these or similar lights were {{brc|24|s}}, {{brc|26|s}}, {{brc|47|s}} and a solitary {{brc|86}}.

In 1985 Class 37s were timetabled to operate over the Cambrian Line for the first time, operating the summer Saturday Only services to {{stn|Aberystwyth}} that had previously been hauled by Class 25s. The Class 37s took over the train from {{stn|Shrewsbury}} and in one case the service was heavy enough to require two of the class in multiple.<ref>{{cite book |last1=Greaves |first1=Simon |last2=Greengrass |first2=Robert |last3=Webster |first3=Neil |title=Loco-hauled travel 1985–86 |publisher=Platform 5 |location=Sheffield |year=1985 |page=16 |isbn=0-947773-02-9}}</ref> While the first year of operation utilised Class 37/0s, from 1986 all but one of the Western Region Class 37 turns were diagrammed for operation by Class 37/4s. These were all allocated to Cardiff Canton, and for the first time included scheduled operation of a train between {{rws|Crewe}} and {{rws|Cardiff Central}}, a service which had previously been the preserve of {{brc|33|s}}.<ref>{{cite book |last1=Greaves |first1=Simon |last2=Greengrass |first2=Robert |last3=Webster |first3=Neil |title=Loco-hauled travel 1986 |publisher=Metro Enterprises |location=Baildon |year=1986 |pages=14–15 |isbn=0-947773-04-5}}</ref> In the following years they were also used on the {{rws|Bristol|Temple Meads}}–Cardiff/Swansea leg of services from {{rws|Portsmouth Harbour}} and then on the [[Heart of Wessex line]].

[[File:Class 37s on oil train.jpg|thumb|Two Class 37/7s on an oil train at Reading]]
Over time they were displaced from most passenger work by new build DMUs such as the ''[[British Rail Sprinter|Sprinter]]'' units, though they still found work in the summer and on secondary services from time to time through the 1990s as traffic demand required. This saw use both on the North Wales Coast and, most remarkably, [[Rhymney line|Cardiff–Rhymney]] local services through to 2006. In Scotland after being displaced from the West Highland and far north routes, 37/4s were used on two diagrams on the {{rws|Inverness}}–{{rws|Edinburgh|Waverley}} route for several years as well as being used to Kyle of Lochalsh in the summer and on Inverness–{{rws|Aberdeen}} services. The final daily work in Scotland was the Fort William ''[[Caledonian Sleeper]]'', this ending in June 2006.

Their freight work similarly reduced, being displaced by higher powered locomotives such as the {{brc|56}} and {{brc|58}} locomotives on coal trains, though they continued on other cargos such as oil tankers for longer.

===After privatisation===
{{more citations needed|section|date=July 2023}}
In the 1980s, many locomotives were refurbished, which has contributed to the Class 37 fleet becoming one of the longest surviving classes on British railways. However, the introduction of {{brc|66}} locomotives meant many 37s were withdrawn or scrapped. [[DB Cargo|English Welsh & Scottish]] and [[Direct Rail Services]] operated small fleets, with several other examples also operated by spot-hire companies. However, second-hand Class 37s have also proved popular in the export market, with some examples operating in Spain and France, serving the construction of those countries' high-speed railway networks. As of 2025, numerous examples of the class are still in mainline service, despite most of them being at least sixty years old.

====Colas Rail====
[[Colas Rail]] owns ex-preservation 37057, 37099, 37116, 37175, 37219, 37254, 37421, all currently operational.

Additionally, Colas purchased 37146, 37188 and 37207 with the intention of returning them to main line duty but, as of March 2020, 37146 is unlikely to receive its intended overhaul and is expected to be sold or used as a parts donor. 37188 was broken up at [[UK Rail Leasing]]'s Leicester depot, in 2019.

Between July 2019 and March 2020, three Colas Rail Class 37s (Nos. 37025, 418, 421) operated peak time loco-hauled services on the [[Rhymney line]] with eight Mark 2 carriages,<ref>{{cite web |url=https://www.itv.com/news/wales/2019-07-03/50-year-old-loco-drafted-in-to-cope-with-demand-in-the-rhymney-valley/ |title=54-year-old loco drafted in to cope with demand in the Rhymney Valley |website=ITV News |date=3 July 2019 |access-date=22 March 2020}}</ref> the first passenger loco-hauled services on the route since 2005, due to a lack of rolling stock caused by the two-year delay on the {{brc|769}} that was scheduled to run services on the route.<ref>{{cite web |url=https://www.railmagazine.com/news/network/class-37s-to-stay-in-wales-into-2020 |title=Class 37s to stay in Wales into 2020? |website=[[RAIL Magazine]] |access-date=22 March 2020}}</ref>

====Direct Rail Services====
[[File:37038 at Crewe Works.jpg|thumb|right|Class 37/0 in [[Direct Rail Services]] livery at [[Crewe Works]] in June 2003]]
[[Direct Rail Services]] (DRS) has a variety of Class 37s operational and others stored. DRS originally purchased and operated a mix of class 37/0s, 37/4s, 37/5s and 37/6s . Most of the DRS 37s were used on [[nuclear flask]] services coming from a host of places including Hunterston, Torness, Heysham, Hartlepool, Sizewell, Bridgwater, Valley and Dungeness, but are now being replaced by {{brc|68|s}}. These are empty or full FNA wagons often containing spent nuclear fuel. Following a review of traction requirements and delivery of its new [[Vossloh]]/[[Stadler Rail|Stadler]] [[Eurolight|UK Light]] Class 68 diesels and [[Stadler Rail|Stadler]] [[Stadler Euro Dual|UK Dual]] {{brc|88}} bi-mode locomotives, DRS has stored, withdrawn or sold most of its Class 37 fleet, apart from the 37/4s.

In July 2016, 37424 was renumbered 37558 and named ''[[Avro Vulcan XH558]]''.<ref>{{cite web |url=http://www.directrailservices.com/news-articles/2016/07/27/drs-open-day-2016-a-great-success/ |title=DRS Open Day 2016 – A Great Success |publisher=Direct Rail Services |access-date=4 August 2016 |archive-date=20 August 2016 |archive-url=https://web.archive.org/web/20160820144425/http://www.directrailservices.com/news-articles/2016/07/27/drs-open-day-2016-a-great-success/ |url-status=dead}}</ref>

DRS Class 37s were hired to power passenger services on the [[Wherry lines]] (Norwich to Great Yarmouth/Lowestoft) for [[Abellio Greater Anglia]] between June 2015 and September 2019, due to a shortage of diesel multiple units, as a result of two serious accidents. Until December 2018 they also hauled passenger services on the [[Cumbrian Coast Line]] on behalf of [[Northern Rail]] (until 2016) and then its successor, [[Arriva Rail North]].

====EWS/DB Schenker====
{{expand section|date=June 2025}}
[[File:EWS 37717.jpg|thumb|37717 in early EW&S livery at St Denys]]
[[File:37401 fort william.jpg|thumb|[[DB Cargo UK|EWS]] maroon 37401 at {{rws|Fort William}}]]
[[File:Weymouth 37670 37401.jpg|thumb|37670 in DB Schenker livery at Weymouth]]
<!-- Section unsourced since May 2024

[[DB Cargo UK|EWS]] usually used Class 37s in pairs, for freight workings. Additionally EWS used the Class 37s on railtours or charter hire to train operating companies. For example, in 2005 Arriva Trains Wales used 37/4 haulage on the Rhymney valley line, from a pool of four locomotives, these locomotives being 37405 (EWS livery), 37411 (BR green livery), 37419 (EWS livery) and 37425 (BR Large Logo). 37419 replaced 37408 ''Loch Rannoch'', which was involved in a collision with parked stock at Rhymney sidings, which was suspected to be caused by vandals. 37408 suffered extensive damage and was written off at [[Toton TMD]] with its power unit removed and used to revive 37422. Its body was later scrapped at [[European Metal Recycling]], [[Kingsbury, Warwickshire]].

By mid-2008, only three EWS Class 37s were still in regular use on the mainline (37401, 417, 422). 37422 was placed in WNTS tactical store pool in September leaving only 37 401 and 417 in traffic. On 16 December, 37 417 suffered serious engine failure and was sent to Eastleigh for storage, resulting in 37401 becoming the only Class 37 to remain in traffic into the new DB Schenker era.

DB Schenker had one operational Class 37/4, 37401, at the time of its rebranding from EWS on 1 January 2009. DB Schenker also had hired locomotives for temporary duties, such as 37 423 from Direct Rail Services (DRS) to cover for failed 37417. DB Schenker 37401 (and DRS's 37 423) were on snowplough duty at Inverness for the winter months. 37401, DB Schenker's sole operational English Electric Type 3 at the time, was reported sounding rough and was later stored, although this did not last long, as it was soon sent to Toton TMD for repairs along with 37406 ''The Saltire Society''.

37401, DB Schenker's most reliable Class 37, was repaired and returned to service. 37406 was returned to service, failing on its first working. 37670 was also returned operational.

37419 was prepared for a return to traffic and repainted into DB Schenker livery, however its long time in store did not help its power unit and it failed with a serious engine fault on its trial run. The locomotive is now operational with DRS.

DB Schenker had the largest route for railhead treatment trains for Autumn 2009 and required Class 37 haulage due to their route availability. Much speculation was surrounding the return of several Class 37s, however DB Schenker was eventually given clearance from Network Rail to use Class 66s and 67s on the routes instead, resulting in the Class 37 plan being ditched despite several of the machines having their air horns moved onto the nose to resolve clearance problems.

Reliability problems plagued 37670 during its short time in traffic and the loco was eventually stored unserviceable.

With the storage of 37670, this meant that (once again) 37401 was the sole operational Class 37 in active service under DB Schenker. To take the strain off 37401, 37425 ''Pride of the Valleys'' was fitted with OTMR safety equipment and was returned fully operational. The locomotive retained in BR blue large logo livery, however (like 37670) it was also plagued with unreliability.

As of summer 2010, DB Schenker Rail UK ceased using Class 37s. -->
[[DB Cargo UK|EWS]] used a number of Class 37s.

In June 2013, DB Schenker offered six Class 37s for sale: 37703, 37714, 37716, 37718, 37800 and 37884. These had been stored out of use at [[Dollands Moor]] after returning from mainland Europe, where they had been working on the construction of a new high speed line.<ref>{{cite web |url=http://www.rail.co.uk/rail-news/2013/more-1960s-redundant-class-37-diesel-locomotives-put-up-for-sale-by-db-schenker/ |title=More 1960s redundant Class 37 diesel locomotives put up for sale by DB Schenker |publisher=Rail.co.uk |access-date=25 March 2014 |archive-date=26 March 2014 |archive-url=https://web.archive.org/web/20140326015743/http://www.rail.co.uk/rail-news/2013/more-1960s-redundant-class-37-diesel-locomotives-put-up-for-sale-by-db-schenker/ |url-status=dead}}</ref> 37703 went on hire/loaned (but still owned by Direct Rail Services) to the Scottish Railway Preservation Society, 37 703/714/716/718 were bought by Direct Rail Services. 37718 was scrapped at CF Booth, Rotherham in July 2015. 37800 and 37884 were bought by [[Europhoenix]] and once restored to working order, went on long term hire to Rail Operations Group in a dual Europhoenix/ROG livery.

<!-- Both sections have not had sources since at least May 2024
====West Coast Railways====
[[File:37 706 British Rail class 37 diesel loco.jpg|thumb|[[West Coast Railways]] 37706 approaching Northam Junction]]
[[West Coast Railways]] (WCR) purchased four locomotives from [[Ian Riley Engineering]] in 2004. The two operational locomotives (nos. 37197 and 37261) were used on charter trains or as standby locomotives for ''The Jacobite'' [[Steam locomotive|steam-hauled]] excursion services from {{rws|Fort William}} to {{rws|Mallaig}} during 2005. These two, along with non-operational 37423, have since been sold to DRS. The fourth (no. 37 235) was for spares.

In late 2007, WCR purchased several non-operational Class 37/5 and Class 37/7s from EWS: nos. 37517, 37668, 37676, 37685, 37706, 37712 and 37710. Of the acquired locomotives 37710 will be used as a source of spares, 37676 and 37712 were the first two returned to mainline. 37676 was named ''Loch Rannoch'' at a special event in [[Carnforth]] Steamtown. 37712 suffered a fire on an empty coaching stock move and was subsequently stored. It is known that major work will need to be done on 37712, however demand exists for chartered Class 37s.

By the end of 2019, WCR had seven Class 37s running in service: nos. 37516, 37518, 37668, 37669, 37676, 37685, 37706 with nos. 37710 as a spares donor and 37517 and 37712 stored.

====Locomotive Services Limited====
Since 2017 [[Locomotive Services Limited]] (LSL) began to acquire a number of class 37s to use alongside its own fleet of [[British Rail Class 47|BR Class 47]]s. As of February 2020 LSL has four on its books and running in service: nos. 37190, 37521, 37667 and 37688. Not all of these are owned by LSL, as some are hired in by the company from their owners, for use on LSL-run trains.-->

====Rail Operations Group====
[[File:On the final journey (geograph 6217754).jpg|thumb|[[Rail Operations Group|ROG]] 37884 hauling Class 313 units through Newport]]
[[Rail Operations Group]] (ROG) leases six Class 37s (37510, 37601, 37608, 37611, 37800, 37884) from [[Europhoenix]] for frequent moves of passenger stock. These have been modified to be able to couple with and operate the brakes on various EMU classes without the need for translator vehicles.<ref>{{cite web |title=Train Operations |url=https://www.railopsgroup.co.uk/train-operations/ |url-status=dead |archive-url=https://web.archive.org/web/20191022092838/https://www.railopsgroup.co.uk/train-operations/ |archive-date=22 October 2019 |access-date=22 October 2019 |website=Rail Operations Group}}</ref>
{{clear}}

==Operators==

=== Summary ===
The following is the 2024 fleet summary of mainline registered locomotives, excluding members on preserved railways.{{citation needed|date=April 2023|reason=Original cite was dated 2007}}

{| class="wikitable"
|-
! Owner
! Number
! Numbers
! Notes
|-
| [[Colas Rail]]
| 8
| 37025*, 37057, 37099, 37116, 37175, 37219, 37254, 37421
|
|-
|[[Europhoenix]]
| 12
| 37510{{efn|group=list|name=Euro|Hired to [[Rail Operations Group]]}}, 601{{efn|name=Euro}}, 608{{efn|name=Euro}}, 611{{efn|name=Euro}}, 800{{efn|name=Euro}}, 884{{efn|name=Euro}}, 901. 
Stored: 37069{{efn|group=list|name=EuroRein|37069, 218 and 423 will be repaired and put back into service in the future}}, 146, 207, 218{{efn|name=EuroRein}}, 407, 423{{efn|name=EuroRein}}
| 37670 was cut up on 9 March 2018; 37188 was cut up on 24 July 2019.
|-
|[[Harry Needle Railroad Company]]
| 5
| 37405, 424-425<ref>{{cite magazine |title=News round up - Harry Needle Railway Company |magazine=Rail Express |date=21 June 2024 |issue=338 |page=20}}</ref>,37607, 610{{efn|group=list|name=HNRC|Hired to Colas}}, 612{{efn|name=HNRC}}
Stored: 37038, 059, 259, 419, 422, 602, 716
| HNRC were originally tasked with locating and overhauling class 37s for Colas.<ref>{{Cite web|url=https://www.railmagazine.com/trains/specifications/golden-oldies-continue-to-play-their-tune?p=3|title=Golden oldies continue to play their tune |website=[[RAIL Magazine]]}}</ref>
|-
| [[Locomotive Services Limited]]
| 7
| 37190{{efn|group=list|stored at the [[One:One Collection]], Margate.<ref>{{cite news |last1=Bailes |first1=Kathy |title=New locomotive exhibit arrives at 1:1 Museum project in Margate |url=https://theisleofthanetnews.com/2021/08/04/new-locomotive-exhibit-arrives-at-11-museum-project-in-margate/ |work=The Isle Of Thanet News |date=4 August 2021}}</ref>}}, 401, 402, 409, 521, 603–604, 609,<ref>{{cite magazine |title=DRS locomotive tender results revealed: HNRC and LSL snap up 20s, 37s and 57s |magazine=Rail Express |issue=309 |date=February 2022 |page=24}}</ref> 667, 688{{efn|group=list|On long-term lease from D05 Preservation Ltd.}}
| 
|-
|[[Loram Maintenance of Way|Loram UK]]
|1
|37418{{efn|group=list|Preserved on hire to Loram Rail <ref name="37418Loram">{{cite web |title=Loram signs agreement for Class 37 locomotive |url=https://www.railadvent.co.uk/2024/02/loram-signs-contract-for-class-37-locomotive.html |website=Rail Advent |access-date=1 January 2025}}</ref>}}, 508
|
|-
|[[Network Rail]]
| 4
| 97301 (37100), 97302 (37170), 97303 (37178), 97304 (37217).
| ERTMS fitted for Cambrian Lines
|-
|[[UK Rail Leasing]]
| 1
| 37905
|
|-
|Vintage Trains
|1
|37240
|
|-
|[[West Coast Railways]]
| 11
| 37516, 518, 676, 668{{efn|group=list|name=ertms|fitted with Hitachi ERTMS/ETCS Equipment for Cambrian Lines in 2015. Not yet used alone on Charters over the line.<ref>{{Cite web |url=https://www.geminirailgroup.co.uk/case-studies/class-37-5-locomotive-upgrades/ |title=Class 37/5 Locomotive Upgrades |website=Gemini Rail Group}}</ref>}}, 669{{efn|name=ertms}}, 685, 706. Stored; 37165{{efn|group=list|name=spare|Spares donor}}, 517{{efn|name=spare}}, 710{{efn|name=spare}}, 712.
| 
|- 
|''Total''
| '''65'''
|
|
|}
{{notelist|group=list}}

=== Fleet list ===
{{Main|List of British Rail Class 37 locomotives}}

==Accidents and incidents==
<!--* On the night of 16–17 December 1965, D6983 while hauling a train was in collision with a derailed freight hauled by [[British Rail Class 47]] D1671 ''Thor'' near Bridgend, South Wales. The driver and second man of D1671 died, and damage to both locomotives was extensive enough that even though each locomotive was barely a year old, they were withdrawn and eventually scrapped. D6983 was the first Class 37 withdrawn and the only one of the class not to be renumbered.{{citation needed|date=June 2023}} Unsourced since June 2023, so now removed-->
* In January 1988, locomotives No. 37671 and 37672 were hauling a freight train that was diverted into a siding at Tavistock Junction, [[Devon]] due to a pointsman's error. The train collided with a wagon, pushed it through the buffers and was derailed.{{sfn|Earnshaw|1993|pp=39, rear cover}}
* On 2 September 2009, a Class 97/3 locomotive operated by Network Rail collided with a Fiat Punto on an unmanned level crossing near Penrhyndeudraeth. The elderly driver of the car was killed in the collision.<ref>{{Cite web |url=https://www.bbc.com/news/10327865 |title=Track lights urged after Gwynedd woman's death |date=16 June 2010 |website=BBC News}}</ref>
* On 12 May 2014, locomotive 37198, stored by [[Network Rail]] on the [[Great Central Railway (heritage railway)|Great Central Railway]] and coupled to a [[Post Office Sorting Van]], ran away for 1.8 miles (2.9&nbsp;km) due to an ineffectively placed wheel scotch. It then struck the end vehicle of a rake of five [[British Railways Mark 1|Mark 1]] coaches.<ref>{{cite web |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/432456/R042015_150521_Loughborough_Central.pdf |title=Runaway and subsequent collision near to Loughborough Central station, Great Central Railway |date=21 May 2015 |work=Rail Accident Investigation Branch |access-date=12 November 2020}}</ref>

==Departmental==
===Network Rail ERTMS project===
[[Network Rail]] restored four Class 37s as part of the [[European Rail Traffic Management System]] (ERTMS) trial project on the [[Cambrian Line]]. The site of the restoration was the [[Barrow Hill Roundhouse]], where ex-[[Harry Needle Railroad Company|HNRC]] locomotives 37100, 37170, 37178 and 37217 were taken in. The restored Class 37s for ERTMS use were re-designated as {{brc|97|3}}, numbered 97301, 97302, 97303 and 97304.<ref>{{cite web |title=About Class 37s - Data Sheet |url=https://www.c37lg.co.uk/class37data |website=Class 37 Loco Group |access-date=31 January 2025}}</ref>

The class was chosen because of its original fitment with both air and vacuum braking, a feature which will allow them to pull both modern freight trains as well as special enthusiast trains. The main work of the locomotives is to pull on-track machines (such as [[ballast tamper|tampers]]) through the ERTMS section.

The 97/3s are based at the newly constructed [[Shrewsbury TMD|Coleham Depot]] for the duration of the ERTMS testing on the Cambrian Line, thereafter they are used to pilot trains not fitted with the ERTMS signalling system.  They are also used to work Network Rail test trains on other parts of the network when not required for ERTMS testing.

These locos were effectively refurbished, having been completely stripped down to bare steel, with reconditioned engines, somewhat updated cabs, all new signalling systems installed (ERTMS in this instance) and extensive re-wiring.

97302, 303, and 304 all remain operational as of August 2022.  97301 is currently stored at [[Railway Technical Centre|Derby RTC]].

==Preservation==
[[File:37901 British Rail diesel loco.jpg|thumb|37901 ''Mirrlees Pioneer'']]
Class 37 locomotives have proven very popular with preservation groups and [[railfan|enthusiast]]s alike. Many have been restored to operational service on [[heritage railway]]s, whilst others are awaiting overhaul or restoration. Notable preserved examples include the first-built locomotive, D6700, and the last,  37308.

A number of the class have been sold out of preservation to mainline operators, including both [[Ruston & Hornsby|Ruston]]-engined prototypes Nos. 37905/6. One locomotive, 37372, has been procured by the [[British Rail Class 23#Preservation|Baby Deltic Project]], for conversion into a replica of a {{brc|23|Baby Deltic}}.<ref>{{cite web |url=http://www.thebabydelticproject.co.uk/#/the-project/4534194461 |title=The Project |publisher=The Baby Deltic Project}}</ref>
{| class="wikitable sortable"
|-
!Pre<br/>[[TOPS]]
!Post<br/>[[TOPS]]
!Final
!Name
!Owner
!Location
!Livery
!Notes 
|-
|-
|align=center|D6607
|align=center|37307
|align=center|'''37403'''
|Isle of Mull
|Privately owned
|[[Bo'ness and Kinneil Railway]]
|BR Blue Large Logo
|Operational <ref name="auto">{{Cite web |url=http://www.srpsdiesel.co.uk/index.html |title=SRPS Diesel Group Home page |website=SRPS Diesel Group}}</ref>
|-
|align=center|D6608
|align=center|37274
|align=center|'''37308'''
|
|Privately owned
|[[Severn Valley Railway]]
|Sky Blue undercoat
|Awaiting overhaul <ref>{{Cite web |url=https://www.svrwiki.com/BR_Class_37_37308 |title=BR Class 37 37308 - SVR Wiki |website=Severn Valley Railway Wiki}}</ref>
|-
|align=center|'''D6700'''
|align=center|37119
|align=center|37350
|(National Railway Museum)
|[[National Railway Museum]]
|[[Great Central Railway (heritage railway)|Great Central Railway]]
|BR Green
|Operational <ref>{{Cite web |url=https://www.gcrailway.co.uk/the-railway/locomotives/ |title=Locomotives |publisher=Great Central Railway}}</ref>
First-built Class 37
|-
|align=center|D6703
|align=center|'''37003'''
|align=center|37360
|Dereham Neatherd High School
|Class 37 Locomotive Group
|UKRL Leicester TMD
|BR Blue
|Undergoing overhaul <ref>{{Cite web |url=https://www.midnorfolkrailway.co.uk/37003 |title=37003 |publisher=Mid-Norfolk Railway}}</ref>
|-
|align=center|D6709
|align=center|'''37009'''
|align=center|37340
|
|English Electric Preservation
|[[Great Central Railway (Nottingham)]]
|BR Blue
|Undergoing restoration <ref>{{Cite web |url=https://www.gcrn.co.uk/node/13 |title=37 009 |publisher=Great Central Railway (Nottingham) Ltd.}}</ref>
|-
|align=center|D6723
|align=center|'''37023'''
|align=center|-
|(Stratford)
|Privately owned
|[[Pontypool and Blaenavon Railway]]
|BR Blue Large Logo
|Undergoing restoration <ref name="auto1">{{Cite web |url=https://www.bhrailway.co.uk/stock-list |title=Stock List |publisher=Blaenavon Railway}}</ref>
|-
|align=center|D6724
|align=center|37024
|align=center|'''37714'''
|[[Cardiff Canton TMD|Cardiff Canton]]
|Heavy Tractor Group
|[[Great Central Railway (heritage railway)|Great Central Railway]]
|Railfreight Triple Grey Metals Sub-Sector
|Operational <ref>{{Cite web |url=https://www.heavytractorgroup.org/about-the-loco |title=About the Loco |website=The Heavy Tractor Group}}</ref>
|-
|align=center|D6725
|align=center|'''37025'''
|align=center|-
|[[Inverness TMD]]
|The Scottish Thirty-Seven Group
|[[Bo'ness and Kinneil Railway]]
|BR Blue Large Logo
|Operational <ref name="auto"/>
|-
|align=center|'''D6729'''
|align=center|37029
|align=center|-
|
|Privately owned
|[[Pontypool and Blaenavon Railway]]
|BR Green
|Operational <ref>{{cite web |url=https://www.bhrailway.co.uk/post/class-37-makes-it-s-debut-on-a-passenger-service-at-blaenavon |title=Class 37 makes its debut on a passenger service at Blaenavon |date=11 May 2025}}</ref><ref>{{cite web |url=https://www.eorailway.co.uk/news/class-37-and-class-03-depart-epping-ongar-railway-for-the-final-time/ |title=Class 37 and class 03 depart Epping Ongar Railway for the final time |work=Epping & Ongar Railway}}</ref>
|-
|align=center|'''D6732'''
|align=center|37032
|align=center|37353
|(Mirage)
|Privately owned
|[[North Norfolk Railway]]
|BR Green
|Operational <ref>{{Cite web |url=https://www.nnrailway.co.uk/portfolio-items/br-class-37-d6732/ |title=BR Class 37 – D6732 |publisher=North Norfolk Railway}}</ref>
|-
|align=center|'''D6737'''
|align=center|37037
|align=center|37321
|(Gartcosh)
|Devon Diesel Society
|[[South Devon Railway (heritage railway)|South Devon Railway]]
|BR Blue
|Undergoing restoration <ref>{{Cite web |url=https://www.southdevonrailway.co.uk/rolling-stock/locomotives/d6737-english-electric-type-3-br-class-37-37-037/ |title=D6737 – English Electric Type 3 – BR Class 37 – 37 037 |work=South Devon Railway |date=3 June 2017 |last1=Johnson |first1=Alan}}</ref>
|-
|align=center|D6742
|align=center|'''37042'''
|align=center|-
|
|
|[[Eden Valley Railway (heritage railway)|Eden Valley Railway]]
|EWS Maroon & Gold
|Awaiting restoration <ref>{{Cite web |url=http://www.evr-cumbria.org.uk/motivepower.htm#37042 |work=Eden Valley Railway, Warcop, Cumbria |title=Motive Power at the Eden Valley Railway}}</ref>
|-
|-
|align=center|D6775
|align=center|'''37075'''
|align=center|-
|
|Privately owned
|[[Keighley and Worth Valley Railway]]
|Railfreight Triple Grey
|Operational <ref>{{Cite web |url=https://kwvr.co.uk/25059-br-type-2-class-25-bo-bo-diesel-electric-2/ |title=37075 BR Type 3, Class 37 CO - CO Diesel Electric |work=Keighley & Worth Valley Railway |date=12 April 2022}}</ref>
|-
|align=center|D6797
|align=center|'''37097'''
|align=center|-
|Old Fettercairn
|Caledonian Railway Diesel Group
|[[Caledonian Railway (Brechin)|Caledonian Railway]]
|BR Blue
|Operational <ref>{{Cite web |url=http://www.crdg.co.uk/locomotives.htm |work=Caledonian Railway Diesel Group |title=Locomotives}}</ref>
|-
|align=center|'''D6808'''
|align=center|37108
|align=center|37325
|
|Privately owned
|[[Crewe Heritage Centre]]
|BR Green
|Awaiting restoration <ref>{{Cite web |url=https://www.crewehc.co.uk/attractions |title=Attractions |work=Crewe Heritage Centre}}</ref>
|-
|align=center|D6809
|align=center|'''37109'''
|align=center|-
|
|ELR Diesel Group
|[[East Lancashire Railway]]
|Railfreight Triple Grey Metals Sub-Sector
|Operational <ref>{{Cite web |url=http://www.elrdiesel.info/fleet-37109.php |work=ELR Diesel Group |title=37109/D6809}}</ref>
|-
|align=center|D6823
|align=center|37123
|align=center|'''37679'''
|
|Privately owned
|Railway Support Services
|Railfreight Triple Grey
|Stored <ref>{{Cite web |url=https://www.railwaysupportservices.co.uk/ |title=Overview |work=Railway Support Services}}</ref>
|-
|align=center|D6842
|align=center|'''37142'''
|align=center|-
|
|
|[[Bodmin and Wenford Railway]]
|BR Blue
|Undergoing overhaul <ref>{{Cite web |url=https://www.bodminrailway.co.uk/the-railway/meet-the-fleet/ |title=Meet the Fleet |work=Bodmin Railway}}</ref>
|-
|align=center|D6852
|align=center|37152
|align=center|'''37310'''
|British Steel Ravenscraig
|Privately owned
|[[Peak Rail]]
|BR Blue Large Logo
|Operational <ref>{{Cite web |url=https://www.railwaymagazine.co.uk/12264/peak-rail-type-3-refreshed/ |title=Peak Rail Type 3 refreshed |work=The Railway Magazine |date=30 September 2019}}</ref>
|-
|align=center|D6869
|align=center|37169
|align=center|'''37674'''
|(St Blaise Church 1445 – 1995)
|Privately owned
|[[Strathspey Railway (preserved)|Strathspey Railway]]
|Railfreight Red Stripe
|Operational <ref>{{Cite magazine |url=https://www.pressreader.com/uk/railways-illustrated/20220104/page/24/textview |title=37674 joins the Strathspey Railway's resident fleet |magazine=Railways Illustrated |via=PressReader |date=February 2022 |issue=228 |page=24 |department=News {{!}} Heritage}}</ref>
|-
|align=center|'''D6898'''
|align=center|37198
|align=center|-
|
|[[Darlington Borough Council]]
|[[Head of Steam]]
|BR Green
|Static display.
Donated to the museum by [[Network Rail]].<ref>{{cite news |last1=Edgar |first1=Bill |title=Historic Class 37 locomotive rolls back into Darlington |url=https://www.thenorthernecho.co.uk/news/19506120.historic-class-37-locomotive-rolls-back-darlington/ |access-date=13 August 2021 |work=[[The Northern Echo]] |publisher=[[Newsquest]] |date=12 August 2021 |archive-url=https://web.archive.org/web/20210813222909/https://www.thenorthernecho.co.uk/news/19506120.historic-class-37-locomotive-rolls-back-darlington/ |archive-date=13 August 2021}}</ref>
|-
|align=center|D6905
|align=center|37205
|align=center|'''37688'''
|Great Rocks
|DO5 Ltd 
|[[Locomotive Services Limited]]
|Railfreight Triple Grey Construction Sub-Sector
|Operational <ref>{{Cite web |url=https://inter-city.co.uk/the-train/ |title=The Train |website=Inter City}}</ref>
|-
|align=center|D6906
|align=center|37206
|align=center|'''37906'''
|
|
|[[Battlefield Line Railway]]
|Railfreight Triple Grey
|Undergoing overhaul <ref>{{Cite web |url=https://www.railwayclubdirectory.com/items-5/battlefield-line-railway |title=Battlefield Line Railway |website=Railway Club Directory}}</ref>
[[Ruston (engine builder)|Ruston]] RK270T engine
|-
|align=center|D6915
|align=center|'''37215'''
|align=center|-
|
|The Growler Group
|[[Gloucestershire Warwickshire Railway]]<ref name="gwr215">{{cite web |url=http://www.gwsr.com/html/locomotives.html |work=Gloucester Warwickshire Railway |title=Locomotives |at=subsection 'diesel' |archive-url=https://web.archive.org/web/20090327200309/http://www.gwsr.com/html/locomotives.html |archive-date=27 March 2009}}</ref>
|BR Blue
|Operational <ref>{{cite web |last=Booth |first=Janine |date=8 June 2023 |title=Gloucestershire Warwickshire Railway marks diesel loco's 25 years in preservation |url=https://www.railadvent.co.uk/2023/06/gloucestershire-warwickshire-railway-marks-diesel-locos-25-years-in-preservation.html |access-date=8 June 2023 |website=RailAdvent}}</ref><ref name="gwr215"/><ref>{{Cite web |url=https://www.gwsr.com/about-us/our-trains |title=37215 |website=Gloucester Warwickshire Railway}}</ref>
|-
|align=center|'''D6916'''
|align=center|37216
|align=center|-
|(Great Eastern)
|Private
|[[Pontypool and Blaenavon Railway]]<ref>{{cite web |url=http://www.pontypool-and-blaenavon.co.uk/pages/LOCOS-DIESEL/locos-diesel.html |title=Diesel Locomotives at Blaenavon |archive-url=https://web.archive.org/web/20080819191935/http://www.pontypool-and-blaenavon.co.uk/pages/LOCOS-DIESEL/locos-diesel.html |archive-date=19 August 2008 |website=Pontypool and Bleanavon Railway}}</ref>
|BR Green
|Undergoing restoration <ref name="auto1"/>
|-
|align=center|D6927
|align=center|'''37227'''
|align=center|-
|
|
|[[Chinnor and Princes Risborough Railway]]
|Railfreight Triple Grey Metals Sub-Sector
|Operational <ref>{{Cite web |url=https://www.chinnorrailway.co.uk/article.php/8/locomotives |title=Locomotives |work=Chinnor & Princes Risborough Railway}}</ref>
|-
|align=center|'''D6948'''
|align=center|37248
|align=center|-
|(Midland Railway Center/Loch Arkaig)
|Privately owned – in custodianship of 'The Growler Group'
|[[Gloucestershire Warwickshire Railway]]
|BR Green
|Operational <ref>{{Cite web |url=https://www.gwsr.com/our-trains/d6948 |title=D6948 |website=Gloucester Warwickshire Railway}}</ref>
|-
|align=center|D6950
|align=center|'''37250'''
|align=center|-
|
|Privately owned
|[[Wensleydale Railway]]
|''Dutch'' Civil Engineers' Grey & Yellow
|Operational <ref>{{Cite web |url=https://wensleydale-railway.co.uk/comings-and-goings/ |title=Comings and Goings |work=Wensleydale Railway}}</ref>
|-
|align=center|D6955
|align=center|'''37255'''
|align=center|-
|
|Privately owned <ref name="gc">{{cite web |url=http://www.gcrailway.co.uk/About_Us/Locomotives.aspx?ID=23 |title=Locomotives – 37255 |first=Paul |last=Taylor |archive-url=https://web.archive.org/web/20120624095846/http://www.gcrailway.co.uk/About_Us/Locomotives.aspx?ID=23 |archive-date=24 June 2012 |url-status=dead |website=Great Central Railway}}</ref>
|[[Nemesis Rail]]
|''Dutch'' Civil Engineers' Grey & Yellow
|Stored
|-
|align=center|D6961
|align=center|'''37261'''
|align=center|-
|(Caithness)
|Privately owned
|[[Bo'ness and Kinneil Railway]]
|
|-
|align=center|D6963
|align=center|'''37263'''
|align=center|-
|
|Privately owned
|[[Telford Steam Railway]]
|BR Departmental Grey 
|
|-
|align=center|D6964
|align=center|'''37264'''
|align=center|-
|
|Privately Owned
|[[North Yorkshire Moors Railway]]
|BR Blue Large Logo
|
|-
|align=center|D6971
|align=center|37271
|align=center|'''37418'''
|An Comunn Galdhealach<br>(Pectinidae/East Lancashire Railway)
|Privately owned – On hire to Loram <ref name="37418Loram"/>
|Derby R.T.C.
|Loram Red and White <ref name="37418Loram"/>
|Mainline Operational
|-
|align=center|'''D6975'''
|align=center|37275
|align=center|-
|(Stainless Pioneer/Oor Wullie)
|
|[[Dartmouth Steam Railway]]
|BR Blue
|Operational
|-
|align=center|D6994
|align=center|'''37294'''
|align=center|-
|
|
|[[Embsay and Bolton Abbey Steam Railway]]
|BR Blue
|
|}

== Models ==
In 1965, [[Hornby Railways]] launched its first version of the BR Class 37 in [[OO gauge]].<ref>{{cite web |url=http://www.hornbyguide.com/class_details.asp?classid=17 |title=Hornby – BR Class 37 (Type 3) 1965 |work=Hornby Railways Collector Guide |access-date=31 January 2020}}</ref>

In 2008, [[Bachmann Branchline|Bachmann]] introduced a couple of versions of the locomotive in OO gauge, which included [[Digital Command Control|DCC sound]]: 37057 with the unofficial name of ''Viking'', and 37698 ''Coedbach'' in two-tone grey [[Railfreight]] Coal livery.<ref>{{cite magazine |title=A sound investment |first=Nigel |last=Burkin |magazine=[[British Railway Modelling]] |pages=84–85 |volume=16 |issue=2 |date=May 2008 |location=Bourne |publisher=Warners Group Publications |issn=0968-0764 |oclc=1135061879}}</ref><ref>{{cite magazine |title=DCC sound 37 hits the right note |magazine=Hornby Magazine |first=Mike |last=Wild |pages=84 |issue=8 |date=February 2008 |location=Hersham |publisher=Ian Allan Publishing |issn=1753-2469 |oclc=226087101}}</ref> Italian company ViTrains released four OO gauge versions of the Class 37 in 2008. These were 37378 in Railfreight red stripe livery, 37371 in Mainline blue livery, 37405 in EWS livery and 37201 in Railfreight metals sector livery.<ref>{{cite magazine |title=Four more 37 variants from ViTrains |first=Mike |last=Wild |magazine=Hornby Magazine |pages=88 |issue=10 |date=April 2008 |location=Hersham |publisher=Ian Allan Publishing |issn=1753-2469 |oclc=226087101}}</ref>

In 2008, [[Graham Farish]] introduced [[British N gauge]] models of 37038 and 37238 in BR blue, and D6707 and D6826 in BR green.<ref>{{cite magazine |title=Graham Farish Class 37/0 |first=Richard |last=Docket ill |magazine=British Railway Modelling |pages=76–77 |volume=16 |issue=3 |date=June 2008 |location=Bourne |publisher=Warners Group Publications |issn=0968-0764 |oclc=1135061879}}</ref><ref>{{cite magazine |title='N' gauge EE Type 3 steps up |first=Mike |last=Wild|magazine=Hornby Magazine |pages=72–73 |issue=9 |date=March 2008 |location=Hersham |publisher=Ian Allan Publishing |issn=1753-2469 |oclc=226087101}}</ref> In 2012, Graham Farish introduced a [[Digital Command Control|DCC-ready]] British N gauge model of 97302 in Network Rail yellow and a Class 37/0 model in EWS livery.<ref>{{cite magazine |title=Farish Network Rail Class 37|first=Nigel |last=Burkin |magazine=British Railway Modelling |pages=88–89 |volume=20 |issue=9 |date=December 2012 |location=Bourne |publisher=Warners Group Publications |issn=0968-0764 |oclc=1135061879}}</ref>

In 2020, Accurascale announced that they would release their own OO gauge Class 37 model in 2023.<ref>{{cite web |last=Burke |first=Fran |date=15 December 2020 |title=A First Look At Our Class 37! |url=https://www.accurascale.com/en-us/blogs/news/a-first-look-at-our-class-37 |access-date=12 March 2023 |publisher=Accurascale }}</ref><ref>{{cite web |last=Burke |first=Fran |date=13 January 2023 |title=Project Update – Class 37 January 2023 |url=https://www.accurascale.com/en-us/blogs/news/project-update-class-37-january-2023 |access-date=12 March 2023 |publisher=Accurascale }}</ref>

== See also ==
* [[Passenger locomotives in use in the UK]]

== References ==

=== Citations ===
{{Reflist}}

=== References ===
* {{cite book |last=Clough |first=David N. |title=British Rail Standard Diesels of the 1960s |date=August 2009 |publisher=Ian Allan |location=Hersham |isbn=978-0-7110-3373-3 |id=0908/B1 }}
* {{cite book |last=Earnshaw |first=Alan |title=Trains in Trouble: Vol. 8 |year=1993 |publisher=Atlantic Books |location=Penryn |isbn=0-906899-52-4 }}
* {{cite book | last = Marsden | first = Colin J. | title = Motive power recognition:1 Locomotives | publisher = Ian Allan Ltd | year= 1981 | location = Shepperton | isbn = 0-7110-1109-5}}
* {{cite book | last = Morrison | first = Brian | title = The Power of the 37s |series= Power Series | publisher = OPC | year= 1981 | location = Headington | isbn = 0-86093-093-9}}
* {{cite book | last1 = Preedy | first1 = Norman E | last2 = Ford | first2 = H L | title = BR Diesels in Close-Up | publisher = D Bradford Barton Ltd | location = Truro}}
* {{cite book | last1 = Williams | first1 = Alan | last2 = Percival | first2 = David | title = British Railways Locomotives and Multiple Units including Preserved Locomotives 1977 | publisher = Ian Allan Ltd | year=  1977 | location = Shepperton | isbn = 0-7110-0751-9}}

==Further reading==
* {{cite book|title=Locomotive Recognition: Class 37s|first1=David N.|last1=Clough|first2=D.&nbsp;I.|last2=Rapson|publisher=Ian Allan|year=1991|isbn=9780711019195|oclc=26632324}}
* {{cite book|title=Class 37s at Work|first=Michael J.|last=Collins|publisher=Littlehampton Book Services Ltd.|location=London|year=1984|isbn=9780711014473|oclc=14931264}}
* {{cite book|title=Looking Back At Class 37 Locomotives|first=Kevin|last=Derrick|publisher=Strathwood|year=2011|isbn=9781905276240}}
* {{cite book|title=Syphon Salute - 50 Years of Class 37s|first=Kevin|last=Derrick|publisher=Strathwood|year=2015|isbn=9781905276752}}
* {{cite book|title=Class 37 Photo File|first=Martin|last=Loader|publisher=Vanguard Publications|year=1998|isbn=9781900872027|oclc=655247051}}
*{{cite book|title=British Rail Main Line Diesel Locomotives|first1=Colin J.|last1=Marsden|first2=Graham B.|last2=Fenn|pages=146–155|publisher=Haynes|location=Sparkford|year=1988|isbn=9780860933182|oclc=17916362}}
* {{cite book |last=McManus |first=Michael |title=Ultimate Allocations, British Railways Locomotives 1948–1968 |publisher=Wirral. Michael McManus }}
* {{cite book|title=Class 37s in South Wales|first=Nick|last=Meskell|publisher=Train Crazy Publishing|location=Blackpool|year=2006|isbn=9780954803575|oclc=171537608}}
* {{cite book|title=Scottish Class 37s|volume=One - The Steam Heat Years|first=N.&nbsp;J.|last=Meskell|publisher=Train Crazy Publishing|location=Blackpool|year=2004|isbn=9780954803513|oclc=190776403}}
* {{cite book|title=Scottish Class 37s|volume=Two|first=N.&nbsp;J.|last=Meskell|publisher=Train Crazy Publishing|location=Blackpool|year=2005|isbn=9780954803544|oclc=190776403}}
* {{cite book|title=Scottish Class 37s|volume=Three - The 1990s|first=N.&nbsp;J.|last=Meskell|publisher=Train Crazy Publishing|location=Blackpool|year=2007|isbn=9780954803582|oclc=190776403}}
* {{cite book|title=BR-EE Class 37 diesel electrics|first=Michael|last=Oakley|publisher=Barton|location=Truro|year=1979|isbn=9780851533629|oclc=16499594}}
* {{cite book|title=Rail Portfolios: Class 37|first=Paul|last=Shannon|publisher=Ian Allan|location=Hersham|year=2005|isbn=9780711030978|oclc=58554935}}
* {{cite book|title=The 37s-Second Series|first=Paul|last=Shannon|publisher=Ian Allan|location=Shepperton|year=1990|isbn=9780711019317|oclc=60085212}}
* {{cite book|title=37s in the Highlands|first=Roger|last=Siviter|publisher=Runpast Publishing|year=1989|isbn=9780946184521|oclc=20691702}}
* {{cite book|title=Diesel Retrospective: Class 37|first=John|last=Vaughan|publisher=Ian Allan|location=Hersham|year=2007|isbn=9780711032002|oclc=85897919}}
* {{cite book|url=http://www.barrowmoremrg.co.uk/BRBDocuments/Locos/Book_no_100_N1_web.pdf|title=Vehicle Diagram Book No. 100 for Main Line Diesel Locomotives|via=Barrowmore MRG|publisher=British Railways Board|location=Derby|date=October 1984|pages=19–22, 36–37, 92–98 (per pdf)}}
* {{cite book|title=Class 37 Locomotives|first=Andrew|last=Walker|publisher=Amberley Publishing|year=2016|isbn=9781445657370|oclc=934603454}}
* {{cite magazine|title=Howay the 37s!|first=Peter|last=Doel|magazine=[[Rail (magazine)|Rail Enthusiast]]|publisher=EMAP National Publications|date=December 1981 – January 1982|page=60|issn=0262-561X|oclc=49957965}}
* {{cite magazine|title=Rolling Stones!|first=Peter|last=Kelly|magazine=[[Rail (magazine)|Rail Enthusiast]]|publisher=EMAP National Publications|date=September 1982|pages=18–21|issn=0262-561X|oclc=49957965}}
* {{cite magazine|title=The Great Eastern Class 37s: The First 25 Years|first1=Ian|last1=Cowley|first2=Graham|last2=Hardinge|magazine=[[Rail (magazine)|Rail Enthusiast]]|publisher=EMAP National Publications|date=October 1986|issue=61|pages=I-XVI|issn=0262-561X|oclc=49957965}}
* {{cite magazine|title=6 of the best|first=David|last=Clough|pages=34–37|issue=106|date=5–18 October 1989|magazine=[[Rail (magazine)|RAIL]]|publisher=EMAP National Publications|issn=0953-4563|oclc=49953699}}
* {{cite magazine|title=All in a day's work: Class 37/4|first=Pip|last=Dunn|pages=22–26|issue=303|date=23 April – 6 May 1997|magazine=[[Rail (magazine)|RAIL]]|publisher=EMAP Apex Publications|issn=0953-4563|oclc=49953699}}
* {{cite magazine|title=Probably the best locomotive in the world!|first=Pip|last=Dunn|magazine=[[Rail (magazine)|Rail]]|issue=309|publisher=EMAP Apex Publications|date=16–29 July 1997|pages=40–45|issn=0953-4563|oclc=49953699}}
* {{cite magazine|title=Re-birth of a classic|first=Pip|last=Dunn|magazine=[[Rail (magazine)|Rail]]|issue=310|publisher=EMAP Apex Publications|date=30 July – 12 August 1997|pages=28–34|issn=0953-4563|oclc=49953699}}
* {{cite magazine|title=Clean and green – a pioneer is honoured at last|first=Pip|last=Dunn|magazine=[[Rail (magazine)|Rail]]|issue=337|publisher=EMAP Apex Publications|date=12–25 August 1998|pages=36–40|issn=0953-4563|oclc=49953699}}
* {{cite magazine|title=A locomotive for all duties|first1=Chris|last1=Leigh|first2=Dave|last2=Lowery|magazine=[[Model Rail]]|pages=18–23, 25–29|issue=4|date=Autumn 1998|location=Peterborough|publisher=EMAP Apex|issn=1369-5118|oclc=173324502}}
*{{cite magazine|title=Masterclass: BR class 37/9s|first=Alan|last=Banks|magazine=[[Model Rail]]|pages=18–24|issue=111|date=December 2007|location=Peterborough|publisher=EMAP Active|issn=1369-5118|oclc=173324502}}

== External links ==
{{commons category|British Rail Class 37}}
* [http://www.c37lg.co.uk/ The Class 37 Locomotive Group] Owners of 37003
* [http://www.thegrowlergroup.org.uk The Growler Group] Class 37 37215, 37248 (custodians)

{{British Rail Locomotives}}
{{Authority control}}

[[Category:British Rail diesel locomotives|37]]
[[Category:Co-Co locomotives]]
[[Category:English Electric locomotives]]
[[Category:Vulcan Foundry locomotives]]
[[Category:Robert Stephenson and Hawthorns locomotives]]
[[Category:Railway locomotives introduced in 1960]]
[[Category:Diesel–electric locomotives of Great Britain]]
[[Category:Standard-gauge locomotives of Great Britain]]
[[Category:Diesel–electric locomotives of France]]
[[Category:Standard-gauge locomotives of France]]
[[Category:Diesel–electric locomotives of Italy]]
[[Category:Standard-gauge locomotives of Italy]]
[[Category:Diesel–electric locomotives of Spain]]
[[Category:Standard-gauge locomotives of Spain]]
[[Category:Co'Co' Diesel Locomotives of Europe]]