Sir John Percival was a tailor who became Lord Mayor of London in 1498. Career. He was a member of the Worshipful Company of Merchant Taylors. In 1486, he became Sheriff of London, sharing the role with Hugh Clopton. In 1498, he became Lord Mayor of London. Personal life. He was the third husband of Thomasine Bonaventure. They had no children together.