Dissident Republicans have already scouted sites for the London Olympics to identify targets for potential terrorist attacks in 2012.
British Security Forces have confirmed to the Irish Independent that a suspected cell from the Oglaigh na hEireann group visited London in February.
The ONH is regarded as the most dangerous of the three dissident IRA groupings and is in the frame for the recent murder of Catholic policeman Ronan Kerr in Omagh.
A four strong scouting party from the ONH was followed around London as they visited and photographed the Olympic venues and other key sites according to the Independent.
Undercover British Army surveillance experts followed the group for three weeks in total.
Two of the scouting party travelled from South Armagh and Monaghan and met with two associates who live in the English capital.
However British security sources do not believe the ONH group, with only 50 members, has the strength or resources to mount a major terrorist attack.
They believe the ONH will target police and military sites in the short term but the risk of an attack by dissidents on Britain was increased last September from moderate to substantial, meaning there is a strong possibility of an attack.