What is known is that Thomas spent a number of years in the English court and married the youngest daughter of Sir Adrian Fortescue, named Frances.

[4] The Chancellor, Archbishop John Alen, attempted to persuade him not to commit himself to such a rash proceeding; but the young lord's harper, understanding only Irish, and seeing signs of wavering in FitzGerald's bearing, commenced to recite a poem in praise of the deeds of his ancestors, telling him at the same time that he lingered there over long.

Goods and chattels belonging to the King's subjects he declared forfeited, and he announced his intention of exiling or putting to death all born in England.

He retreated to his stronghold at Maynooth Castle, but in March 1535 this was taken by an English force under Sir William Skeffington by bribing a guard, while Thomas was absent gathering reinforcements to relieve it.

Thomas had wrongly assumed that his cause would attract overwhelming support, in particular from Catholics opposed to Henry VIII's English Reformation.

He was still a formidable opponent, and Grey, wishing to avoid a prolonged conflict, guaranteed his personal safety and persuaded him to submit unconditionally to the King's mercy.

Silken Thomas's revolt caused Henry to pay more attention to Irish matters, and was a factor in the creation of the Kingdom of Ireland in 1542.