He became Earl of Desmond in 1463, when his father died.
From "A New History of Ireland," edited by Moody, Martin & Byrne, vol 3, ISBN 0-19-821739-0, 1976, p 9: He was executed at Drogheda in 1468. p. 10:
The districts from Youghal to Cork harbour and on the western shore of the latter were in the hands of the elder Desmond line, but much land was held by independent Old English lords. The Courceys still [in 1534] used the title of Lord Courcey; the alleged viscountancies claimed by the Roches (Viscount Fermoy) and the Barrys (Viscount Buttevant) had no legal basis, though they came to be recognized by the crown. Barrys and Roches, like other great Old English families in County Cork, were highly gaelicised, employing brehons and patronising bardic poetry.
Tried for high treason before Parliament at Drogheda under John Tiptoft, Earl of Worcestor, for extorting Coin & Livery, of which he had been frequently accused, and had attainted persons by Act of Parliament for making the accusation. He was beheaded at Drogheda, 15 Feb 1467, 7 Edw IV.
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