The sitter was the third and youngest son of James Campbell, 2nd Earl of Loudoun and his wife Margaret, daughter of Hugh Montgomerie, 7th Earl of Eglinton. On 29th March 1720 he married Jane, daughter of David Boyle, 1st Earl of Glasgow. His career in the army started shortly after his appointment in 1708 as Lieutenant-Colonel of the 2nd Dragoons of Scots Greys, when he commanded the dragoons at the Battle of Malplaquet in 1709. He took the initiative when the outcome of the battle appeared uncertain and, ignoring his orders not to move, charged with his dragoons right through the enemy lines. He continued to serve with the regiment until the Peace of Utrecht when he entered politics as an active supporter of the Hanoverians. In 1727 he became MP for Ayrshire. George II appointed him Major-General and a Groom of the Bed-Chamber, and in 1738 he was made Governor of Edinburgh Castle. When war broke out again in 1742 he accompanied the King to Germany as commander of the cavalry and for his brave cavalry charge at the battle of Dettingen in 1743 he was invested with the Order of the Bath on the battlefield. He was fatally wounded at the Battle of Fontenoy on 30th April 1745.