The sitter was the son of Charles, 5th Lord North (1635-1691; see lot 50) and was elected to the House of Lords in 1699. In 1703 he was made a Colonel in the 10th regiment of the foot, and the following year he fought with Marlborough at the Battle of Blenheim, where he was wounded and lost his right hand. In 1705 William married Maria Margaretta van Ellemeet, the daughter of Vryheer van Ellemeet, Treasurer of Holland. The couple commissioned pendant portraits by the Dutch artist Constantyn Netscher (private collection).
In 1711, William was made Lord Lieutenant of Cambridgeshire, and in 1712 he became Governor of Portsmouth. His Tory-Jacobite sympathies resulted in his being commissioned by James Edward Stuart, the Old Pretender (1688-1756) as commander-in-chief for London/Westminster, and he was given the title Earl North, Lord Regent. He was associated with the Atterbury plot of 1721-22, a planned armed invasion of Britain on behalf of the Old Pretender, but was arrested on the Isle of White while making his escape and sent to the Tower in October 1722. After being released on bail a year later, he retired from public office until 1728, when after repeated solicitations he took a Spanish army commission and converted to Catholicism.