Background
He was the son of James Johnstone, 1st Earl of Hartfell and Henrietta Douglas. He succeeded to the Earldom of Annandale and Hartfell on the death of his father in 1672.
He was the son of James Johnstone, 1st Earl of Hartfell and Henrietta Douglas. He succeeded to the Earldom of Annandale and Hartfell on the death of his father in 1672.
He was restored to favour on making confession and was created an Extraordinary Lord of Session in 1693, and a Lord of the Treasury. He received a pension for services in connection with Glencoe inquiry. He was appointed a Knight of the Thistle in 1704, joint Secretary of State from March–September 1705.
He opposed the Union, but later served as a representative peer from 1709-1713.
He was Keeper of the Great Seal of Scotland from 1714-1716. William was married twice: first on 1 January 1682 to Sophia Fairholme, daughter of John Fairholme of Craigiehall, and second on 20 November 1718 to Charlotte Van Lore Bempde, daughter of John Vanden Bempde of Hackness.