Real IRA planned London attack that would have ‘overshadowed’ Omagh bomb, spy claims

David Rupert, an FBI agent, also claimed the British secret services did not want to arrest dissident Republican leader, Michael McKevitt. The American told BBC’s Spotlight show his spook handlers had no interest in the prosecution of the Republican chief.

“MI5 wanted to keep the intelligence gathering going forever,” Mr Rupert said.

The American spied on both the Continuity and Real IRA before ultimately providing evidence against Michael McKevitt in 2003, when he was convicted of directing terrorism by a Dublin court.

Rupert ran a bar in Leitrim in the mid-90s at the time he was recruited to work for MI5. He had managed to earn the trust of dissident Republican leaders who believed he could help raise much needed funds Stateside.

The group he infiltrated, the Real IRA, was responsible for the Omagh bomb which claimed the lives of 29 civilians and two unborn babies in 1998. Now Rupert claims an even bigger attack was on the cards.

“The hit is going to be directed specifically at something like troops or the London centre financial district.

"To make a big enough splash to overshadow anything that could have happened at Omagh,” Mr Rupert told a handler in an email.

The former FBI man also says the British had a deep understanding of how the Republicans in charge were thinking at the time.

"MI5 were wonderful to work with. I would call them on my way to a meeting with McKevitt and they would tell me that he's probably going to ask you this or that and when he does, here's what we want you to tell him, and they were pretty accurate," Mr Rupert said.

The undercover agent says MI5 and the FBI had different priorities when it came to dealing with Mr McKevitt. The British wanted to focus on intelligence ahead of everything else.

"MI5 wanted to keep it going forever. (But) The FBI won. I mean they won the argument.

“It was more important to MI5 to have a thumb on the pulse than it is to go arrest a couple of people and prosecute them,” Mr Rupert said.

The ex-trucker also gave details about the technology used by spooks and how he now views his actions at the time.

“We used an encryption system when I sent an email it went to both handlers. I was just doing a job. And doing a job that I viewed as doing for good to stop them from killing people," he said.

The Real IRA merged with other Republicans to form the New IRA in 2012. The February shooting of Det Ch Insp John Caldwell in Omagh, County Tyrone was the most recent attack on police officers in Northern Ireland, which was claimed by the group.