He also held the prebends of Lyme Regis, Calstock, Bedminster, and St Mary Redcliffe, Bristol, and the living of St. Edmond's, Salisbury.
A court preacher in high favour with Henry VIII, he helped the King write Assertio Septem Sacramentorum,[2] a reply to Martin Luther, and then published his own work on the subject in December 1523.
Powell was one of the four theologians selected to defend the legality of the marriage of Catherine of Aragon, in connection with which he wrote the "Tractatus de non dissolvendo Henrici Regis cum Catherina matrimonio" (London).
He was discharged from the proctorship of Salisbury in January, 1534, and in November he was attainted, together with John Fisher, for high treason in refusing to take the oath of succession, deprived of his benefices, and imprisoned in the Tower of London.
A dialogue in verse was published shortly after, "The Metynge of Doctor Barnes and Dr. Powell at Paradise Gate and of theyre communicacion bothe drawen to Smithfylde fro the Towar" (London, 1540), in the British Museum.