Seized of the manors of Glyn, Beagh, and Cappagh, and attainted 18 Henry VIII, and again, with his son, 2 Elizabeth I.

For supporting his cousin Thomas, the elder brother of Gerald the 14th Earl of Desmond, who had been disinherited by his father, but who laid claim to the earldom but lost, he and his son were attainted in 1560.21

He and his son were captured, taken prisoner and condemned to death as traitors for taking the field in the cause of the imprisoned earl of Desmond. The son was executed. The father barely escaped the same fate by a legal technicality. The father was pardoned on account of some doubts concerning the statute which made burning of houses treason in Ireland. On 13 Feb 1569 the parliament in Dublin passed an act entitling her majesty to the lands, etc. in Munster belonging to Thomas Fitzgerald, knight of the valley, in the county of Limerick and Thomas, his son and heir at law apparent, who had been executed. The Glin estate at that time consisted of lands and castles. In this area the knight had no fewer than 20 castles. 21

With a view to determining the precise extent of the Glin estate the crown had an inquisition taken on Mar 7 1572 concerning the knight of the valley's lands. The head of the knight's son and heir was on the spikes of LImerick castle, Glin and other important castles were battered and occupied, the entire estate was confiscated by the crown, and Glin's onetime powerful champion the earl of Desmond was in the Tower of London. No surprise that Thomas died within 3 years.21