The present work is a previously unrecorded sketch for the central figure of Copley's monumental The Siege of Gilbraltar, now in the Guildhall Art Gallery.
The finished picture records the climax of events in 1782, the Spanish and French having held siege to the English-held rock for over three years. On the morning of 13 September the Spanish advanced ten specially built 'battering ships' which dropped anchor about 1000 yards from the English garrison. A furious exchange ensued but the defenders nestled in the rocks were difficult targets compared with the Spanish, whose attack all but ceased by the evening. The scene at dawn the next day, described in the Annual Register of 1782, was one of carnage. The event was a turning point in the siege and a large relief fleet under Admiral Howe pierced the blocade the following month.
Copley started work on his commission in 1783 but did not complete the picture until 1793. Enormous work went into the composition and detail of the scene and numerous sketches - some, like the present work, in oil - survive. The only other recorded study of General Eliott is of bust-length format, with a more finished head (London, National Portrait Gallery, no. 170). The sitter was a particularly distinguished soldier who had taken charge of the English forces on Gibraltar in 1775 . He was created Lord Heathfield in 1787 and the three-quarter-length portrait of him by Reynolds (London, National Gallery) has long been held to be one of that artist's masterpieces.