Lord Eglinton is recorded as having sat to Reynolds on 24 and 27 March and 6 April 1784. This is likely to have been for a full-length portrait of the sitter in Highland Dress. Accordingly, it is thought that this unfinished portrait is either a preliminary study for the full-length portrait of Lord Eglinton, or a fragment of the full-length which was never completed. If the latter is true, it may have come into the collection of George IV already partly cut down and may conceivably have been reduced further in 1829 before being framed as an oval. The photograph in Richard Redgrave’s inventory shows that at some stage during the nineteenth century the image was overpainted, affecting both the background and the dress. A miniature copy in enamel was made by Henry Bone in 1797.

Archibald Montgomerie, Eleventh Earl of Eglinton joined the army as a young man and, at the outbreak of the Seven Years’ War, raised the Montgomerie's Highlanders (or 77th Regiment) and was elected Lieutenant-Colonel. Montgomerie succeeded to the Earldom on the death of his elder brother, Alexander, in 1796. He was also the patron for the poet, Robert Burns and they kept in close contact until his own death in October 1796.

Reynolds’s expert handling of his materials is evident in the dramatic modelling of the sitter’s face and the wonderful feather in the sitter’s plumed bonnet which appears to flutter in the Highland breeze. Although Reynolds has historically been criticised for his lack of technique, it would be impossible to argue that this portrait is anything but the work of a master draftsman.