Michael McKevitt's conviction for directing the Real IRA and being a member of an illegal organisation is a landmark decision affecting those who oppose the peace process.
The Irish Republic's Special Criminal Court, a handsome Georgian building on the edge of the riverside markets in Dublin, is no stranger to bizarre and dramatic trials.
This is where the Northern Ireland MP Peter Robinson was prosecuted for his part in a surreal incursion onto the soil of the Irish Republic back in 1986.
Businessman David Rupert won McKevitt's trust
It was from the dock here that the 19th century patriot Robert Emmet made his celebrated speech in the moments after he was condemned to death, a speech which has inspired generations of rebels.
But even this oldest and most celebrated of courts has rarely seen anything to compete with the trial of Michael McKevitt.
He was the first person in the history of the Irish state to be charged with directing terrorism - an offence created as a reaction to the shock and revulsion which followed the Omagh bombing in 1998.
In effect Ireland's police and prosecution service was arguing that Mr McKevitt - who owned a fish and chip in the border city of Dundalk - was the head of the Real IRA, the most active and most violent of the dissident republican groups which oppose the peace process.
They will regard his conviction on that charge as a body blow to the small but dangerous organisations which oppose the peace process in Northern Ireland.
Those who have been behind a persistent bombing campaign both there, and on the British mainland.
Michael McKevitt was a senior figure in the provisional IRA for many years - the organisation's quartermaster, responsible for hiding and transporting its huge and deadly arsenal around Ireland.
His wife Bernadette is the sister of the republican icon Bobby Sands, the first IRA man to die in the hunger strikes of the early 1980s.
He fell out with the mainstream republican movement led by Gerry Adams over its peace strategy and became perhaps the most important figure in the shadowy and dangerous world of the dissidents.
Security experts say his downfall was due to his sudden need to start dealing with the tricky business of raising money, when his real expertise lay in handling and hiding weapons.
That led him into a meeting with David Rupert, a giant American businessman who at 6ft 7ins and 20 stone, must be one of the most physically imposing witnesses to testify at the Green Street courtroom.
Mr Rupert was not just a wealthy American who had become interested in the extreme fringes of Irish paramilitary politics.
He was an informer, working for the FBI, MI5 and the special branch of the Irish police, paid to infiltrate the ranks of the dissident republicans.
The fact that he found it so easy to do so, suggests perhaps that the Real IRA is desperate for money.
The "directing terrorism" offence was created in the wake of Omagh
Mr McKevitt was not as cautious as you might expect for a man attempting to raise funds for a deadly paramilitary campaign, who might have expected to be under heavy surveillance.
He left his legal team with only two strategies - to claim that he had never actually met Mr Rupert and to suggest that the American had simply invented his testimony for cash; or to blacken the giant informer's name.
To that end, there was a microscopic scrutiny of Mr Rupert's past dealings as a haulage contractor, with the occasional colourful excursion into such areas as his brief flirtation with life as a wrestler.
His tax affairs were also closely examined.
In the end though, it did Michael McKevitt no good.
The three judges of the Special Criminal Court, who sit without a jury, decided that he was a key figure in the real IRA and not simply as he portrayed himself, - the owner of a popular fish and chip shop in the border city of Dundalk.
The dissident republican movement has been dealt a serious blow - but already there are warnings that that blow is not fatal, and that the threat from organisations like the Real IRA has not gone away.