Morier was a Swiss military and sporting painter who started working for William Augustus, Duke of Cumberland (1721-65) in 1747, when he painted a series of pictures of troops under his command. From 1752 until 1764 he was employed as ‘limner’ (painter) to the Duke on an annual salary of £100; his name also appears regularly in Royal accounts from 1764 to 1767. In the mid-1760 he also executed a series of horse pictures for the sitter of this portrait, who was said to be 'horse mad' and published in 1761 a 'Method of Breaking Horses, and Teaching Soldiers to Ride'. The Earl of Pembroke is shown here in 1764 when he was made Colonel of the Ist Royal Dragoons, which uniform he wears, with a black tricorn hat. There are troops practicing in the middle distance.