He was created Earl of Wiltshire, in the Peerage of England, by Henry VI of England on 8 July 1449, for his fidelity to the Lancastrian interest. In 1451 he became Lord Deputy of Ireland; the next year he succeeded his father in earldom of Ormond and was additionally appointed Lord Lieutenant for ten years. In 1454, he was constituted Lord High Treasurer of England and made a Knight of the Garter 1459
Information needing clarification
Councillor to the Lancastrian Prince of Wales - noted as needing a source in Wikipedia and not listed amongst his titles/posts by Richardson, although he is listed as "in the retinue of Richard, Duke of York" in 1441.
Location conflict - Battle of Towton (29 March 1461) was in North Yorkshire. Richardson says James was taken prisoner at the battle and executed 1 May 1461 at Newcastle. The Wikipedia article on Eleanor Beaufort says "After Towton, he was a proscribed as a traitor and was captured in the same year at Cockermouth and executed there in 1461." A month later could be considered "in the same year" but the phrasing from the Wikipedia article implies that he was not taken prisoner at Towton, and Newcastle and Cockermouth are a fair distance apart (based on Wikipedia articles on Newcastle and Cockermouth).