English: Portrait of Lady Emma Hamilton, as Cassandra, half length, in a white robe, a laurel wreath crowning her head.

The life of Emma Lady Hamilton, whose beauty and vivacious character took her from humble origins as the daughter of an illiterate blacksmith to become the mistress and later wife of the diplomat, antiquarian, collector and vulcanologist Sir William Hamilton (1730-1803), the King's Minister Plenipotentiary at the Bourbon Court in Naples, and later mistress of the celebrated naval hero, Lord Horatio Nelson, was both extraordinary and, in the end, tragic. The beauty that captured the hearts of both Hamilton and Nelson exerted a similarly magnetic attraction on the imagination of several of the leading artists of the day and none more than Romney. Romney had first met her when she was still the mistress of his friend, the Hon. Charles Greville (1749-1809), a keen art collector who was later responsible for introducing her to his widowed uncle Sir William Hamilton. Greville had brought her to Romney's studio in Cavendish Square to sit for the portrait that was engraved as Nature (Frick Collection, New York) and she soon became Romney's favourite muse and the model, providing the inspiration for dozens of fancy portraits drawn from the worlds of literature and mythology.

In this portrait Romney portrays Lady Hamilton as Cassandra, daughter of King Priam and Queen Hecuba of Troy in Greek mythology. Cassandra's beauty caused the God Apollo to grant her the gift of prophecy, but when she failed to return his love Apollo put a curse on her so that no one would ever believe her predictions. Combining deep understanding with powerlessness, Cassandra exemplified the tragic condition of mankind.

William Hayley (1745-1820), the celebrated poet and author of Life of Romney, in whose possession this picture is first recorded, was a close friend of the artist, to whom he had been introduced in 1776, and was also admired by Lady Hamilton who claimed to have heeded the advice that he gave in his didactic poem Triumph of Temper, of 1781, in which he sought to teach young women the virtues of a pleasant nature.