The sitter was the second but only surviving son of David, 1st Earl of Portmore, and his wife Katherine, daughter of Sir Charles Sedley, Bt., and mistress of King James II. Portmore was a Member of Parliament for Wycombe (1726) and Andover (1727-30), and a founding Governor of the Foundling Hospital. He was Knighted in June 1732 and married in the same year Julia, daughter of Roger Hele of Halwell, Devon, and widow of the 3rd Duke of Leeds. Portmore was famous in high society for the splendour of his dress and equipages; Wraxall noted that 'when nearly 80 he retained his activity of body, with many personal graces, and the most polished manners' (cited in G.E. Cokayne, The Complete Peerage, X, p. 605). This portrait was executed in 1758. A portrait of his second but only surviving son, Charles, 3rd Earl of Portmore (1747-1823), painted by Reynolds in the following year, was sold in these Rooms on 18 June 2008, lot 195, for £265,250.
For a portrait of the sitter as a child, with his elder brother, David Colyear, Viscount Milsington, see lot 46.