High Quality Content by WIKIPEDIA articles! Thomas Cranmer (2 July 1489 – 21 March 1556) was a leader of the English Reformation and Archbishop of Canterbury during the reigns of Henry VIII, Edward VI and, for a short time, Mary I. He helped build a favourable case for Henry`s divorce from Catherine of Aragon which resulted in the separation of the English Church from union with the Holy See. Along with Thomas Cromwell, he supported the principle of Royal Supremacy, in which the king was considered sovereign over the Church within his realm.