The sitter was the son of Charles James MacDonnell of Kilkee and his wife Elizabeth, daughter of Captain Christopher O'Brien. He was evidently the 'Carlos Mae Donnel' (see J. Ingamells, ed. A Dictionary of British and Irish Travellers in Italy 1701-1800, New Haven and London, 1997), recorded in Venice between 12 May and 7 June 1757, with Francis Hutchinson, probably also from Ireland; Thomas 'Condei'-who can be fairly securely identified as Thomas Conolly of Castletown (of whom Mengs supplied three portraits); and William 'Zaiman', whose identity cannot as yet be established. The four presumably spent the ensuing winter in Rome, since the versions of Conolly's portrait are dated 1758. MacDonnell was back in Ireland by 1760, when he married his kinswoman, Catherine, daughter of Sir Edward O'Brien, 2nd Bt., of Dromoland. He purchased Killone Abbey, Ennis from his maternal uncle in 1764, renaming this New Hall and adding a five bay main block to the earlier house. He was Lt-Colonel of the Co. Clare Militia Dragoons, and Member of the Irish Parliament for Ennis from 1768. This portrait is closely comparable with those of Thomas Conolly and Lord Garlies (see S. Roettgen, Anton Raphael Mengs, 1728-1779, I, Munich, 1999, nos. 201-2, the third in a private collection, and 213) and like the former may date from the winter of 1757-8.