The sitter was a Scottish lawyer and politician who sat in the House of Commons between 1774 and 1801. He was the second son of Archibald Stuart of Torrance in Lanarkshire and Elizabeth, daughter of Sir Andrew Myreton of Gogar, Bt. He studied law at Edinburgh and became a member of the Scottish Bar. He was employed by James Hamilton, 2nd Duke of Hamilton as tutor to his children and through his influence was in 1770 appointed keeper of the Signet of Scotland. Stuart represented Lanarkshire in Parliament between 1774 and 1784 and was appointed to the Board of Trade in 1779. In 1790 Stuart was elected as M.P. for Weymouth and Melcombe Regis. He married Margaret, daughter of Sir William Stirling of Ardoch, Bt., and had three daughters. On the death of his brother in 1796 Stuart inherited the estates of Torrance. A year later he inherited the estates of Castlemilk. He published a Genealogical History of the Stewarts [sic] in 1798 and asserted that the Stuarts of Castlemilk were the head of all Stuarts.
Stuart was painted by Sir Joshua Reynolds circa 1778 (sold Sotheby's, London, 5 December 2013, lot 212). A slightly larger portrait of the sitter by Cosway, signed and dated 1790, was in the John Pierpont Morgan (1837-1904) Collection, sold Christie's, London, 24-27 June 1935, lot 282. It was formerly in the collection of Edward Joseph Esq. and exhibited at the Burlington Fine Arts Club, 1889, no. 76.