A brother of one of the men blamed for the Omagh bomb atrocity has been jailed for 12 years for trying to buy weapons and explosives in Lithuania.
Irishman Michael Campbell was arrested in an undercover operation in the Baltic state of Lithuania after handing over cash to buy a sniper rifle, detonators and timers for the Real IRA.
The 39-year-old was convicted by Judge Arunas Kisielus after a two-year trial in the city of Vilnius.
He was arrested in January 2008 following the operation involving the British, Irish and Lithuanian intelligence agencies, which believe the explosives would have been used to mount a terror campaign in Northern Ireland and on the British mainland.
Prosecutors are still seeking the extradition of his brother Liam Campbell and Brendan McGuigan from the Irish Republic.
Liam Campbell is seeking to go before the Supreme Court in London to challenge a civil court ruling which held him liable for the 1998 Omagh bomb, which killed 29 people including a woman pregnant with twins.
Campbell was arrested after a six-year sting orchestrated by MI5.
Video footage and intercepted communications showed he paid 6,000 euros (£5,200) for high-grade explosives, grenade launchers, detonators, AK-47s and a special assassin's rifle, to Lithuanian agents posing as arms dealers.
He was charged with supporting the splinter group by attempting to smuggle firearms, ammunition, and explosive devices from Lithuania to Ireland.
Campbell - from the Upper Faughart area near Dundalk, Co Louth in the Irish Republic, close to the border with Northern Ireland - maintained his innocence and claimed he was the victim of entrapment.
Irmantas Mikelionis, chief prosecutor of the Organised Crime and Corruption Investigations Department of the Prosecutor General's Office, said the explosives could have been used for bombing in London.
"If we failed to stop Mr Campbell, we would put in danger the lives of innocent people," he said.
Mr Mikelionis warned undercover officers risked their own lives during the sting.
"The dangers of being disclosed, the danger of being accused for co-operation with secret services were hanging in the air each time they contacted the members of the terrorist group," he said.
"We are happy we had no painful consequences."
Secretary of State for Northern Ireland, Owen Paterson, said Campbell's conviction was another excellent example of what can come from the high levels of co-operation between countries across Europe and beyond in combating terrorism.
"I am very pleased with this verdict and would like to congratulate the Security Service and the Lithuanian authorities who have collected the evidence that the Court in Lithuania has clearly found to be both convincing and compelling," he said.
"I have no doubt that this will have dealt a blow to RIRA but we are not complacent and we remain determined to do all that we can to bear down on those who are the enemies of the whole community throughout the United Kingdom."
The case centred on a courageous undercover agent, known as Robert Janine, who for years risked his life to provide his MI5 handlers with vital intelligence about the activities of dissident republicans' plans.
In one chilling audio recording, Campbell is heard discussing how easy it would be with the type of equipment on offer to plant a bomb in London and escape.
"You imagine us getting over to England if you'd ten of them and ten clocks in a holdall. You imagine, with a six-hour timer we could be over to London and back.
"Just tick, tick, tick - gone. Leave it anywhere," he said.
Prosecutors said his actions would have created real threats to society.
Mr Mikelionis said authorities in Vilnius were still awaiting the extradition of Campbell's brother and McGuigan, who are both wanted for questioning in relation to the arms smuggling operation.
Campbell, a farmer from Upper Faughart, Co Louth, has been in custody in Northern Ireland since May 2009 when he was detained on foot after crossing the border. His case is due to by mentioned in the Laganside Courts Complex in Belfast on November 18.
An extradition hearing against McGuigan, of Omeath, Co Louth, is expected to be heard in Dublin's High Court next week.