Half-brother of Sir William Fitzwilliam. Made a gentleman of the Privy Chamber in 1519 and present at the Field of the Cloth of Gold. Knighted in 1522. Lieutenant of the Isle of Man in 1525. Undertook a number of diplomatic missions on behalf of Henry VIII. Married the daughter of Sir John Gage. Appointed Privy Councillor in 1539. Took part in the French campaign of the mid-1540s. Appointed a guardian of Prince Edward and Princess Elizabeth just before Henry's death.