Shamefully copied from wiki, but I read it elsewhere, so it must be true.
In May 1535, the new pope, Paul III, created Fisher Cardinal-Priest of San Vitale, apparently in the hope of inducing Henry to ease Fisher's treatment. The effect was precisely the reverse, Henry forbade the cardinal's hat to be brought into England, declaring that he would send the head to Rome instead. In June a special commission for Fisher's trial was issued, and on Thursday, 17 June, he was arraigned in Westminster Hall before a court of seventeen, including Thomas Cromwell, Anne Boleyn's father, and ten justices. The charge was treason, in that he denied that the king was the Supreme Head of the Church of England. Since he had been deprived of his position of Bishop of Rochester by the Act of Attainder, he was treated as a commoner, and tried by jury. [ handy.] The only testimony was that of Richard Rich. [ What's wrong with Wales...?] John Fisher was found guilty and condemned to be hanged, drawn, and quartered at Tyburn.
However, a public outcry was brewing among the London populace who saw a sinister irony in the parallels between the conviction of Fisher and that of his patronal namesake, Saint John the Baptist, who was executed by King Herod Antipas for challenging the validity of Herod's marriage to his brother's divorcée Herodias. For fear of John Fisher's living through his patronal feast day, that of the Nativity of St John the Baptist on 24 June, and of attracting too much public sympathy, King Henry commuted the sentence to that of beheading, to be accomplished before 23 June, the Vigil of the feast of the Nativity of St John the Baptist. His execution on Tower Hill on 22 June 1535, had the opposite effect from that which King Henry VIII intended. John Fisher's beheading created yet another ironic parallel with that of the martyrdom of St John the Baptist who was also beheaded; his death also happened on the feast day of St Alban, the first martyr of Britain.