Background
He was the son of Colonel Thomas Mottley, a Jacobite adherent of James II in his exile, who entered the service of Louis XIV, and was killed at the battle of Turin in 1706. His mother was Dionisia, daughter of John Guise of Ablode Court, Gloucestershire. John was born in London, was educated at Archbishop Thomas Tenison"s grammar school in the parish of Street Martin-in-the-Fields, and obtained a clerkship in the excise office in 1708.