In 1534 Garret Og FitzGerald was summoned to England where Henry had him incarcerated in the Tower of London. His eldest son Thomas rebelled against the king but an army of 2,300 overran the Fitzgerald castle at Maynooth and the garrison was forced to surrender. They were all executed with the exception of Thomas' infant half-brother. Silken Thomas was executed in 1537.

Terror stricken, the Anglo-Irish lords were keen to show loyalty to the king and when parliament reconvened it quickly passed laws similar to those already passed in England, making King Henry VIII head of a state Church. In 1541 Henry VIII was declared King of Ireland by the subservient Irish parliament.