He was born in County Meath, the third of seven sons of Sir Christopher Plunket, who married in 1403 Janet Cusack, the heiress of Killeen Castle, Dunsany. Christopher was created 1st Baron Killeen about 1426, and founded a prominent Anglo-Irish dynasty. It was said that Thomas was "bred to the law": he and his younger brotherRobert were the first two of numerous lawyers and judges in the Plunket family.
Career
Thomas became Serjeant-at-law, who at that time was the senior legal adviser to the Crown, in 1434. He was entrusted with levying subsidies in 1447, and with surveying the royal mines in 1450. He was made a justice of assize in County Meath, and was entrusted with the defence of the county in 1456. There is some evidence that he was admitted to Lincoln's Inn in 1452-3, although the name is spelt "Blonket" in the records. During the Wars of the Roses Thomas, like most of the Anglo-Irish gentry of the Pale, was a supporter of Richard of York; he accompanied him to England in 1460 and was knighted. After the triumph of York's son, King Edward IV in 1461, Plunket was appointed Lord Chief Justice, but was forced to contest the position with his predecessor, Sir Nicholas Barnewall. He was reappointed in 1463 and confirmed in office in 1468 jointly with John Chevir. , Plunket's burial site. He died on 12 June 1471, bequeathing the sum of £100 to Christchurch Cathedral, Dublin. He was buried in Rathmore Church, where an impressive tomb was erected to the memory of Thomas and his second wife Marian Cruise. Rathmore Church is now a ruin, but some traces of the tomb are said to still be visible.
Marriages and children
He married firstly Genet Cusack, and by her had one son who probably predeceased him. He married secondly Marion Cruise, daughter and heiress of Sir Christopher Cruise of Rathmore, County Meath, and in her right became Lord of the Manor of Rathmore. His second marriage, though advantageous, was said to be a love affair. There are several romantic stories about the marriage, and a celebrated ballad, "The Song of Mary Cruys", describing how Thomas as a young barrister in London restored Marion, then a penniless refugee in England, to her rightful inheritance. How much truth there is in the story that Marian and her mother were forced to flee from their home in fear of their lives after her father's murder is uncertain, but violence was endemic in fifteenth century Ireland, as it was in England, so the story may have some basis in fact. He and Marian had five children:
Edmund, who inherited Rathmore but died without issue
