The re-mergence of the present portrait represents an exciting addition to Batoni's oeuvre, having passed erroneously in the early part of the 20th century through the New York salerooms as a work by George Romney. One of the many of the young Englishmen who sat to Batoni on the Grand Tour, little biographical information is known about the Thomas Thornhill (1735/5-1800). He succeeded to his uncle's estates at Fixby, Yorkshire and in 1779 married Eleanor Lynne. Prior to this, c. 1761-4, Thomas undertook a European tour in the company of his younger brother, George, who had a house at Diddington. Thomas is recorded at Capua on 8 February and 12 March 1761 traveling with the Swiss apothecary, intellectual and poet, Jean-Baptiste Tollot acting as their guide (J. Ingamells, A Dictionary of British and Irish Travellers in Italy 1701-1800, New Haven, 1997, p. 938). At Paris, they made the acquaintance of and befriended, Laurence Sterne. A final reference records the purchase of four paintings from the marine painter, Joseph Vernet by 'M. Thornhill, cadet' on 17 May 1764 and a further two more in 1766 (Léon Lagrange, Joseph Vernet et la Peinture au XVIII siécle, Paris, 1864, pp. 343-46).
The Thornhills were descended from an ancient family of Anglo-Danish landholders in Yorkshire. Much of their holding was in the Calder Valley between Pontefract and Dewsbury. The family fought with Harold at the Battle of Stamford Bridge 1066 and their ancestor Gamall is mentioned in the Domesday Book 1085. The Thornhills settled and established themselves near to Dewsbury at Thornhill Lees. They also held the sub manor of Midgley, hence the similarity between the Arms of Midgley and Thornhill. Fixby Hall was modernised by Thomas Thornhill in the mid-18th century and as part of these renovations, he built the Orangery as a wedding present to his bride Eleanor Lynne. Thomas's eldest son, also called Thomas, inherited the estate and notably employed Richard Oastler, the social reformer as Steward to the estate. Thomas's sister, Clara, eventually inherited Fixby and also bought Rushton Hall in Northamptonshire. She became a personal friend of Charles Dickens and it is thought that he gained his inspiration for Haversham Hall in Great Expectations from his visits. The Thornhill family lived full time at Fixby Hall until 1809 when they moved to Norfolk and the building was divided into three livings.