John Fisher is usually associated with Erasmus, Thomas More and other Renaissance humanists. His life, therefore, did not have the external simplicity found in the lives of some saints. Rather, he was a man of learning, associated with the intellectuals and political leaders of his day. He was interested in the contemporary culture and eventually became chancellor at Cambridge. He had been made a bishop at thirty-five, and one of his interests was raising the standard of preaching in England. Fisher himself was an accomplished preacher and writer. His sermons on the penitential psalms were reprinted seven times before his death. With the coming of Lutheranism, he was drawn into controversy. His eight books against heresy gave him a leading position among European theologians.
In 1521 he was asked to study the problem of Henry VIII's marriage. He incurred Henry's anger by defending the validity of the king's marriage with Catherine and later by rejecting Henry's claim to be the supreme head of the Church of England.
In an attempt to be rid of him, Henry first had him accused of not reporting all the "revelations" of the nun of Kent, Elizabeth Barton. John was summoned, in feeble health, to take the oath to the new Act of Succession. He and Thomas More refused because the Act presumed the legality of Henry's divorce and his claim to be head of the English church. They were sent to the Tower of London, where Fisher remained fourteen months without trial. They were finally sentenced to life imprisonment and loss of goods.
When the two were called to further interrogations, they remained silent. Fisher was tricked, on the supposition he was speaking privately as a priest, and declared again that the king was not supreme head. The king, further angered that the pope had made John Fisher a cardinal, had him brought to trial on the charge of high treason. He was condemned and executed, his body left to lie all day on the scaffold and his head hung on London Bridge. More was executed two weeks later.
~from Saint of the Day, Leonard Foley, O.F.M.