Thomas Cromwell served as the king's main advisor from 1532 to 1540. He was the one who finally succeeded in getting the king his divorce. It's possible that Cromwell was the mastermind behind the whole English Reformation [source: Britannica].
Cromwell took over after Cardinal Wolsey's fall from grace. Cromwell was a politician, brought up from Parliament to serve the king. He came to full power when he figured out a way to annul Henry's marriage to Catherine without the pope's permission: Remove the pope's power from England. Cromwell succeeded in getting Parliament to pass the Act of Supremacy that made Henry the head of the church. He disbanded monasteries and did away with the taxes paid to Rome. He effectively removed Catholicism from England, establishing England as a sovereign state.
With Cromwell's adept maneuvering, the king was able to leave Catherine and marry Anne Boleyn. Had the marriage not imploded, Cromwell may have kept his position. But as it turned out, he made a big mistake: After the death of Henry's third wife Jane Seymour, Cromwell convinced Henry to marry Anne of Cleves, of German royal lineage, for political reasons. Henry couldn't stand Anne, and he had the marriage annulled almost immediately. That was the beginning of Crowell's end.
The bad marriage separated Cromwell from the king, and Cromwell's enemies (he was a politician so he had many) set to work. While working to remove the influence of Roman Catholicism from England, Cromwell had occasionally aligned himself with the Lutherans, who were calling for reform in the Catholic Church. The Lutherans were considered heretics, and Henry had published papers denouncing them. Even after the break from the Church, Lutheranism was against English law. After Cromwell lost the king's support, his enemies used this connection to the Lutherans to convince the king that Cromwell was a heretic.
Thomas Cromwell was beheaded for heresy in 1540. He never received a trial.
Cromwell was a powerful man during the reign of Henry VIII. But the next execution on the list did away with one of the most noted individuals in all of English history: Thomas More.