On his fourth constitutional challenge, Denis Riordan finally caught the public imagination by challenging the Government's decision to appoint the former Supreme Court judge, Mr Hugh O'Flaherty, to the European Investment Bank.

A 53-year-old lecturer in marine communications at the Limerick Institute of Technology (LIT), with no formal legal training, Mr Riordan has become something of a specialist in taking High Court challenges on constitutional grounds, once saying that he objected to the manner in which the Constitution was being destroyed.

He represents himself in court and researches his cases at the "massive law library" at the University of Limerick. He says he has read every High Court and Supreme Court judgment since the 1920s, looking for precedent to back up his claims.

Small in stature, he says he was a loner in school and was bullied for the privilege. From a farm in Caherline, Co Limerick, he went as a boarder to St Flannan's in Ennis, where he detested sport. "The vast majority were playing games and I was the oddball, the odd one out. They tend to bully the individual who is a loner."

After school, he qualified as a radio officer and went to sea for five years with Marconi Marine, a company providing radio officers to ships. Back on shore, he worked for Burroughs Machines in Dublin and Digital in Galway, returned again to sea and, since 1978, has lectured at LIT.

"When I was at sea you were much governed by regulations and if you did not abide by those regulations, you lost your job," he said.

He has cast himself in the role of small guy against the system and the latest action has touched a nerve, bringing in letters of support.

"Up to now they would probably have thought of me as a bit of a looney, frivolous. This would have come across from what was said about me in the court and suddenly they are getting an insight into the fact that there might be truth in what I have been saying all along," he said.

One letter-writer sent £10, saying: "You have lots of fans out there. Hang in there and go for it."

Like most Irish people, he has moaned at the perfidy of politicians but says his electioneering and High Court challenges are an acting-out of his views. "That is the problem of society. We all talk but we do nothing," he said.

One of his letter-writers agrees, saying that unlike their Irish counterparts, "French governments live in fear and dread of their electorate".

He has run as an independent candidate in two general elections and two European elections, originally complaining about the dual mandate system which allows a person to be a TD and an MEP simultaneously.

Now he also cites the expenses regime, the introduction of the tax amnesty in 1993 and the regulation that election candidates who fail to get 25 per cent of the quota must pay their own expenses, whereas those over the threshold are reimbursed by the Exchequer.

"I have to pay my own expenses and I also have to contribute to theirs. That is totally unjust."

His challenges so far have failed, both in the High Court and Supreme Court, and attracted little attention other than, as he said himself, that he was perceived as a nuisance and a crank. "The small guy does not matter," he said.

Married and a father of three, he lives on the edge of Limerick city, off the Cratloe Road. This week, before presenting a 30-page submission at the High Court, he stayed with sympathisers who have been involved in child-custody cases.

"They have been damaged by the system and, in particular, by the judicial system and that is why they offer their assistance."

The first challenge he took was in 1994 when he claimed there was no constitutionally appointed head of the Government if both the Taoiseach and the Tanaiste were absent from the State.

In 1997 the President of the High Court, Mr Justice Costello, rejected his claims that the Family Law (Divorce) Act 1996 and the divorce Amendment of 1995 were unconstitutional. In May 1998 he failed in a High Court attempt to halt the referendum on the Belfast Agreement after securing leave to challenge its constitutionality.

He says he is not anti-divorce nor against the agreement, rather that his concern is with the Constitution as the supreme law of the State and "what prevents us from being like Iraq or other countries".

"If I did not have that, I would have been locked up already."