On the list of pictures painted by Gainsborough for George, Prince of Wales this portrait appears at £126. On the same list, and at the same price, is a full-length portrait of the Prince ‘with a Horse sent to Gen.ll St Leger’. Both portraits were exhibited at the Royal Academy in 1782 and seem to have been conceived as companion pieces. The portrait of the Prince is now at Waddesdon Manor.

The elaborate saddle depicted, decorated with the star of the Garter, is the same as that in the portrait of the Prince. The Prince had given St. Leger the saddle, insisting that it should be shown in the picture. The portrait was engraved by Dupont and published in 1783 with a dedication to the Prince of Wales. Gainsborough made some changes to the painting, most noticeably enlarging it on the left, right and top, presumably on finding that the horse was uncomfortably cramped.

St Leger rose up the military ranks and was made a Colonel in 1793. He was promoted to Major General in 1795 and died in India commanding the 80th Regiment of Foot. He was a great companion of the Prince of Wales, who described him as ‘one of ye best fellows yt. ever lived’.