Charles Fitzroy was a politican and army officer, who was appointed Ensign in the 1st Foot Guards in 1752, Captain in 1756 and Lieutenant-Colonel in 1758. He served in the Seven-Years War. He also held various household appointments including Groom of the Bedchamber to George II and George III (1760-2), Vice-Chamberlain to Queen Charlotte (1768-82) and Groom of the Stole to the Prince of Wales (1780-97). This portrait was presumably painted for Queen Charlotte in around 1785. The sitter is shown in peer's robes, with his natural hair powdered and set like a wig. 

This is the only portrait by Benjamin Burnell in the Royal Collection, although another portrait by Reynolds which depicts the same sitter around 25 years earlier (400974).