Probably Jonathan Richardson, the Younger (1694-1771);
Probably his posthumous sale, Langford and Son, London, 18th February 1772, lot 45 ('Richardson Senior, His own portrait');
James Broun-Ramsay, 1st Marquess of Dalhousie (1812-60), before 1861;
Lady Susan Georgiana Broun Bourke (1837-98), by whom brought to Colstoun House, Haddington (according to an old handwritten label on the reverse);
By descent in the Broun family at Colstoun House to 2017.
Literature
J. Kerslake, Early Georgian Portraits. National Portrait Gallery, London 1977, vol. 1, pp. 228 and 231, under cat. no. 706, reproduced vol. 2, plate 674.