(Updated September 2014) Carnegie, a younger son of the admiral sixth Earl of Northesk, entered the Navy in 1771 and became a captain in 1782. From 1788, after the death of his elder brothers, he was styled Lord Rosehill and he succeeded to the earldom in 1792. As captain of the 'Monmouth' during the Nore mutiny of 1797 he was sent by their committee of delegates as an emissary to the king but, their requests being denied by message, did not return in person to his ship as they had demanded. In 1803 he was appointed to the 'Britannia', 100 guns, initially under Cornwallis off Brest but remained in her when he became a rear-admiral in April 1804 (with Charles Bullen then joining him as her captain, see BHC2854) and was sent to reinforce Calder off Cadiz in August 1805. 'Britannia' thus came under Nelson's command on his return to that station and was seventh ship in his weather line at Trafalgar on 21 October 1805 (though in fact lying slightly out to port from it at the time of the attack), where Carnegie's seniority also made him the often-forgotten third-in-command, after Collingwood. He was criticized for being slow into action, probably unfairly since 'Britannia was old, notoriously slow and long out of dock, but she saw close fighting, mainly with the Spanish 'Santisima Trinidad' (130 guns), suffering 42 killed but only ten wounded. He also did sterling work in the storm that followed, taking crews off prizes ordered to be destroyed. For his services he was made a Knight of the Bath and also received the flag officer's gold medal, of which Collingwood's (see MED0159) is the only other one from Trafalgar, since Nelson's was stolen and probably melted down in 1900. He stayed ashore from 1806 but rose by seniority to Admiral of the White and Rear-Admiral of Great Britain in 1821. From 1827 to 1830 he was commander-in-chief at Plymouth and on his death was buried with Nelson and Collingwood in St Paul's Cathedral.

This portrait shows him, probably standing, wearing peer's robes over rear-admiral's full-dress uniform,1795-1812 pattern, with his right arm just visible resting on something. It is now a traditional 30 x 25 inch canvas but reduced from a larger one by cutting and folding round a new stretcher. It is unlined and bears a fine large painted inscription on the back, 'Earl of Northesk / T Phillips pinxt / 1805'. It is also a reused canvas, originally bearing a small-scale equestrian subject in the same orientation, since the head of a horse shows through the panelled background by Northesk's left shoulder (viewer's right). These features suggest it is the 'kit-cat' - normally 36 x 28 inches with one arm showing - noted in the NPG transcript of Phillips's sitter's book for 9 June 1805. The same source records another 'whole length' on 4 April 1807 (that is,of similar size, not 'full-length'), painted for 15 guineas, as the one exhibited at the RA in that year, which suggests the dates are those on which the pictures were finished and approved.

At the time they were done Phillips was a rising society portraitist, elected ARA in 1804 and RA in 1808. According to Samuel Redgrave his portraits were 'characterised by simplicity of style and truthful finish, solid, and carefully executed'. That of Byron, the Romantic poet (in the NPG collection), is especially well known. From 1804 to his death in 1845 he lived and practised at 8 George Street, Hanover Square, having taken it over from the even more fashionable Sir William Beechey RA, who lived there from 1795. Beechey therefore presumably painted Nelson, in 1801 (see BHC2892), in the same studio that Phillips later did Northesk. The Northesk family sold his Trafalgar medal, documents and other memorabilia, and other items relating to his naval career at Sotheby's, London, on 13 December 1994.