Anti-terror squads are examining the threat from an Irish republican cell operating in England, as Britain prepares to host a series of major events on the world stage.
Ahead of April's Royal wedding, a planned state visit by US president Barack Obama in May and next year's London Olympics, some southern-based counter-terrorism teams have been moved from concentrating on Islamic terrorism to being tasked with the Republican threat.
The Irish Observer has learned that Cobra, the Government's emergency committee, is now meeting three times a week, with some sessions chaired by the Prime Minister himself.
An Irish republican cell is thought to be operating in the UK for the first time in 10 years, many of those sent to England are White Lillie’s, active terrorists who have no previous convictions.
The biggest threat is thought to come from a group called Oglaigh na hEireann, in what could be the first Irish cell working in England for some ten years.
However, an attack is not believed to be imminent and the dissident threat not as dangerous as that from radicalised Muslims in Britain linked to Al Qaeda.
Some of these groups are thought to be planning a massacre based on the attacks which devastated Mumbai in 2008, when scores were killed in shootings and bombings across the city.
Irish terror groups were previously thought to have been too small and inexperienced to pose a threat on the mainland, but they are now regarded as a real concern for security at the Olympics.
A source told the Irish Observer: 'As the Games get closer the appetite for risk will diminish.
'The plan will be to disrupt and deter plots, making sure they don't get off the ground, rather than letting them run to gather evidence and get convictions in court.'
In September, Home Secretary Theresa May disclosed the threat level to Britain from Irish-related terrorism had risen from moderate to substantial, meaning an attack is a 'strong possibility'. The threat from international terrorism remained set at severe.
It followed a warning from the head of MI5 that dissident Irish republicans could attempt to mount a new wave of terrorist attacks on the British mainland.
David Cameron is said to be chairing some meetings of the Cobra emergency committee; while Theresa May has disclosed the threat level to Britain from Irish-related terrorism has risen from moderate to substantial
Jonathan Evans, the director-general of the Security Service, said there had been a 'persistent rise' in 'activity and ambition' by dissident groups in Northern Ireland over the past three years.
A report on the day of the publication of David Cameron’s National Security Strategy document – which said Britain is living through an ‘age of uncertainty’ – also warned of a reborn dissident threat from Irish Republicans.
The IRA splinter groups were ranked alongside Al Qaeda sympathisers as having the potential to carry out a major terrorist ‘spectacular’.
Dissident Republicans carried out several attacks in Northern Ireland last year. The report said that Irish terror groups posed a ‘serious and persistent’ danger.
By October last year, there were 37 attacks in the north, compared with 22 in 2009.
A senior security official confirmed that Irish dissidents were believed to be capable of carrying out a major ‘spectacular’ on the mainland but declined to discuss the intelligence behind that claim.
