The man taking the High Court challenge to Mr Hugh O'Flaherty's appointment in Europe is a familiar face around the Four Courts.
Mr Denis Riordan always represents himself in court and despite no legal training has brought a series of constitutional cases against the State.
A lecturer in marine communications at Limerick Institute of Technology, he lives near Redgate, Co Limerick.
Mr Riordan (53) once said he had never applied to be a member of a political party: "Politics is the art of lying. I'm interested in the law." He stood as an independent in Limerick East in the general elections in 1987 and 1997, receiving 80 and 112 votes respectively. In 1994 he stood for the European Parliament, receiving just over 500 votes.
However, it is his constitutional challenges that have brought him to public attention.
In 1994 he took a High Court case claiming the Taoiseach and Tanaiste could not both be absent from the State at the same time. He lost the case and his Supreme Court appeal in November 1997.
The same month, he failed in a High Court challenge claiming that the 14th Amendment of the Constitution Act, 1995, on divorce, and the Family Law (Divorce) Act, 1996, were both repugnant to the Constitution.
The Belfast Agreement referendum was the next challenge. The High Court refused to grant him an injunction halting the poll.
In October 1998 he went to the Supreme Court seeking an order preventing the Government from amending Articles 2 and 3 as provided for in the referendum. At the same time he also appealed the decision on the divorce amendment.
Both appeals were dismissed.
The Supreme Court also rejected Mr Riordan's claims that the appointments of Mr Alan Dukes as a member of the Government, Miss Justice Carroll as chairwoman of the Commission on Nursing and Mr Justice McCracken as sole member of a tribunal of inquiry were unconstitutional.
His claims that the existence of operations of the Office of the Tanaiste from January 1993 to April 1997 were unconstitutional and that Mr John Bruton acted illegally by allowing the use of public funds and the office of the Tanaiste to continue unabated when he became Taoiseach in December 1994 were dismissed.