Cromwell was one of the strongest and most powerful proponents of the English Reformation. He helped to engineer an annulment of the king's marriage to Catherine of Aragon so that Henry could lawfully marry Anne Boleyn. Henry failed to obtain the Pope's approval for the annulment in 1534, so Parliament endorsed the king's claim to be Supreme Head of the Church of England, giving him the authority to annul his own marriage. However, Cromwell subsequently charted an evangelical and reformist course for the Church of England from the unique posts of Vicegerent in Spirituals and vicar-general.