From time to time a judgment emerges from the courts that has reverberations around the political system. The threat from Mr Justice Peter Kelly to jail ministers for failing to provide appropriate care for at-risk children was one, though that threat was averted.

But the jailing this week of Liam Lawlor by Mr Justice Thomas Smyth, a judge who has not been in the public eye before, is likely, in the long run, to have an even greater influence on political culture.

As this judgment, delivered in the most unequivocal terms, was discussed among the legal confraternity, one anecdote emerged that illustrates the style of this very private man.

One of his early cases involved a dispute over Garda allowances. The length of time it took to travel from point A to point B emerged as a crucial issue in the case. The following morning Mr Justice Smyth revealed he had gone out the previous night and walked the distance himself, and he presented the information on the time it took to stunned barristers.

This thoroughness and attention to detail have been hallmarks of his work both as a barrister and a judge. It was evident in his judgment earlier this week, when he quoted liberally from the transcripts of the Flood tribunal, citing chapter and verse, as he detailed Mr Lawlor's successive failures to comply with requests from the tribunal for information.

"He'll take documents home and say he'll read them. And he will, carefully. Not all judges do," said one senior counsel who has appeared before him.

This mastery of detail stems from his practice as a barrister, where he specialised in planning and local government law, appearing on the side both of planners and developers. He represented the State in the long-running Bula mining case, where he was tied up for about two years. He was also in the Arcon planning appeal, which involved a huge amount of complex and technical detail about mining. His grasp of this impressed all involved.

He is also considered one of the experts in environmental law. Along with the former attorney general, Dermot Gleeson, he represented the Hanrahan family in their epic legal battle with the chemical company Merck Sharpe & Dohme, which they lost in the High Court and eventually won in the Supreme Court. The Hanrahans' legal team was working pro bono (on the basis that there was no charge if the case was lost).

However, his legal career began as a solicitor. Originally from Carlow, he was educated in Limerick and at UCD and qualified as a solicitor in 1963. He was assistant secretary to the Incorporated Law Society before being called to the Bar in 1968. He became a senior counsel in 1977. He is married with four grown-up children.

No one was surprised at the trenchant nature of the Lawlor judgment. "He'd be tough. He would take a view and go for it and to hell with the consequences," said a senior counsel. "He would not be afraid to take an unpopular decision. This decision has turned out to be very popular, but he would have no great eye to the great appeal court in the media."

Nor would Mr Justice Smyth be concerned with courting favour from politicians. As long ago as 1988, when he was a senior counsel, he castigated politicians for failing to legislate to protect the architectural heritage of Dublin.

Speaking to a symposium on the future of the city, organised by the Incorporated Law Society, he criticised the fact that listed buildings were being pulled down by bodies supported by public money, and added that the Supreme Court had drawn attention to the need for reform of the law on compensation loopholes in 1983.

"This information was in the Custom House within hours of the judgment," he said then. "Now, almost five years later, there has been no movement from the leviathan, despite periodic groans and moans in the interim from members of the Oireachtas of varying political hues."

This moral indignation when politicians do not do their duty was evident in his ringing declaration this week that Mr Lawlor's failure to co-operate with the Flood tribunal, set up by the Oireachtas of which he was a member, was "a disgrace".

As well as ringing with moral indignation, his judgment in the Lawlor case was marked by quotations from Shakespeare. This came as no surprise to those who know him. "He is passionate about the theatre," said a friend. "He'd go to London a lot to the theatre. And if he was going, say, to Titus Andronicus, he'd read the play beforehand."

His own political sympathies lie with Fine Gael, and he was appointed, along with Catherine McGuinness, to the High Court in 1996 by the Fine Gael-led coalition. However, appointments made at that time were seen as very much on merit, and no one doubts that he could have been nominated by any government.

Almost immediately he was allocated a case that turned out to be even longer than the Bula case, an insurance case involving a company called Superwood, which went on for more than two years. "So Tom Smyth's influence on jurisprudence has only started recently," said a friend at the Bar.

This is likely to follow the description "strict but fair" that he has used himself. "He is a man who likes brevity," said a colleague. "He is courteous, but very decisive. He gets to the point quickly and makes decisions quickly."

"He is not easily shifted if he comes to a view," said another senior counsel. "He is a hard enough man to persuade."

Unlike many judges, he is often sceptical of plaintiffs in personal injury cases, and would not be among the most liberal members of the judiciary when dealing with defendants in the Court of Criminal Appeal.

He works long hours and expects others to do the same. At the end of last year he listed the Lawlor case for hearing on December 30th and 31st, the Saturday and Sunday of the New Year weekend. This was later postponed because he could not get court stenographers, but it typified his attitude to work.

If involved in a long-running case, starting at 11, he will hear other cases between 9 a.m. and 11, which is very unusual in the High Court, and he will sit late.

Along with the theatre and literature, his other passion is gardening. His garden at his home in Sutton is described as magnificent. He has a large greenhouse and enjoys growing vegetables. "He might get up at six in the morning and garden," said a friend and colleague. "Tom would be into eating something that was in the ground that morning," said another friend.

Although not seen as clubbable or outgoing, if working away from Dublin he would always inquire where there was a good restaurant, and he keeps "a bit of a cellar". He does not drive a car.

One senior counsel who has appeared before him summed up his attitude to the reaction to this week's events. "He would not seek the limelight. But he would not shun it either. That would be his philosophy of life."