He had departed for London to study under the Philadelphian history painter and second president of the Royal Academy, Benjamin West, but as the son of Connecticut governor Jonathan Trumbull and a former aide-de-camp to George Washington, he had been arrested as a spy and charged with treason.
It was only thanks to the intervention of West, a particular favourite of George III who personally raised the matter with the king, that he was released after eight months in prison and deported back to America. Three years after the end of hostilities, Trumbull, who was blind in one eye, would return to complete his apprenticeship.
In 1794, a grateful and now successful John Trumbull visited London again, this time armed with his miniature portrait of his teacher's elder brother, William.
William West (1724-1808), a cooper by trade, owned several hundred acres in Chester County, Pennsylvania, and, at the time this picture was painted in Philadelphia in 1793, was a member of the Pennsylvania legislature.
On July 27, 1794, Benjamin West wrote admiringly about the portrait to his brother, whom he had not seen for over 30 years: "Mr Trumbull is arrived in London with Mr Jay, he has presented me with a small portrait of yourself; time has brought you a great resemblance of our father. I am very happy with the present."
This reference to the 4 x 3in (10 x 8cm) miniature from West's correspondence was known, but the whereabouts of the picture remained a mystery until it reappeared at auction in Devon in December. There it was catalogued as "a portrait miniature inscribed on label verso William West of Chester County, Philadelphia, elder brother of Benja West, painter. Painted by J. Humbert Phil 1793."
Even with the misreading of the signature, it should have been enough to raise bidding well above the £100-200 estimate, but the Philip Mould art dealership were fortunate to secure it for less than £200. When removed from its original turned wooden frame, Trumbull's signature was found on the back of the painting to confirm the find.
Approximately 250 Trumbull miniatures painted on mahogany panels are extant.
Philip Mould's Dover Street gallery has recently sold the picture to an American private collector for a price thought to be in the region of £15,000.
By Roland Arkell