He invented the "equals" sign. It appears that he afterwards went to London, and acted as physician to King Edward VI and to Queen Mary, to whom some of his books are dedicated. He was also controller of the Royal Mint and served as Comptroller of Mines and Monies in Ireland.[3] After being sued for defamation by a political enemy, he was arrested for debt and died in the King's Bench Prison, Southwark, by the middle of June 1558.