Raymond Moulton Seághan O'Brien (29 December 1905 – 31 March 1977) was a British-born American businessman, founder of the far-right Irish United Christian Nationalist Party and a pretender to the extinct Earldom of Thomond and the Barony of Ibracken.
Although his mother and step-father divorced a few years later, O'Brien had been raised to believe that Guy was his true father and was devastated to find out this was not the case, causing him to have an identity crisis.
[4] O'Brien appealed to the Irish authorities for the recognition of his title and that same year a Mexican court issued a judgement decreeing that he was indeed the Earl of Thomond.
Following this, he wrote personally from New York to the Taoiseach of Ireland, Éamon de Valera, asking whether he would be allowed to use the titles of Earl of Thomond and Baron Ibracken.
Thomas Sadleir was contacted again who told the Irish government that "there was nothing in law to prevent a man assuming and bearing any name he wished whether that name be in the form of a title or otherwise, provided that in doing so he did not infringe on the rights of some other individual".
The Southend Times in Britain published an interview with Count Howard d'Angerville, who had been appointed Honorary Dalcassian Envoy and Minister to England by "His Highness Prince O'Brien of Thomond".