IT was around noon last Saturday when I received a phone call from a former British military intelligence officer which was to lead a day later to one of the most daring -- and illegal -- adventures by undercover army officers in the history of the Irish Troubles.

That phone call was part of a chain of events which would lead to the St Patrick's Day break-in by British Army spies into the Special Branch offices of the RUC in Castlereagh in Belfast -- supposedly the most secure security force barracks in western Europe. Their aim was simple: to steal secret documents relating to a spy they had been running within the ranks of the IRA. They pulled it off.

The military intelligence officer asked if I could help him . He was worried that the Irish Sunday Tribune newspaper -- with which the Sunday Herald has a close working relationship -- was about to 'out' a friend called Kevin Fulton (not his real name). Fulton is a British Army soldier sent deep under cover within the ranks of the IRA -- a prize agent for Britain. The threat to expose him would have signed his death warrant. The Tribune had no intention of 'outing' Fulton.

It is unclear how the rumour started, but Fulton is no longer a friend of the British state, so the claims could have been a nasty piece of black propaganda put about to frighten him. He has recently turned whistleblower and has been co-operating with investigations into some of the biggest intelligence scandals in the history of Northern Ireland's 'dirty war'. This included devastating claims that the RUC effectively allowed the Omagh bomb to go off in 1999, killing 29 people, despite receiving warnings from him that the atrocity was planned. The RUC's motive was allegedly to preserve the cover of a highly placed double-agent within the Real IRA.

Late last Saturday I spoke to Fulton and reassured him that the Tribune had no plans to 'out' him. But a few hours later other rumours began to circulate that Fulton was planning to 'out' the British Army's star agent within the IRA in revenge for his cover being put in jeopardy. It was this that led directly to the raid on Castlereagh a night later. The rumours filtered all the way up to the very highest echelons within the Ministry of Defence even though Fulton had no intention of 'outing' the agent.

The agent who Fulton was thought to be about to 'out' is a senior IRA man code-named Stakeknife. Unlike Fulton, he is not 'one of the good guys'. He isn't a British agent inserted into the IRA, he is a IRA gunman who turned double-agent for an estimated £75,000 a year from the army through a bank account in Gibraltar. And he's been in the pay of the British for around 30 years.

Stakeknife's role has been intensely scrutinised over the past 18 months. The Scotland Yard inquiry team investigating alleged collusion between British security forces, police and terrorists, led by Met Commissioner Sir John Stevens, has been unofficially sniffing around this shadowy character, and has spoken to former British Army personnel who know of his activities.

The Stevens team are about to complete their mammoth investigation, due out around the end of April, and there has already been jittery speculation that some element of the Stevens report might refer to Stakeknife. No one in British intelligence wants that kind of information to come out. So the thought that the whole house of cards could have come tumbling down even before the Stevens Inquiry wrapped up -- if Fulton opened his mouth -- appears to have been too much to take. Hence the break-in at Castlereagh barracks at 10.11pm last Sunday to remove all traces of Stakeknife from Special Branch files.

At the barrack's checkpoint, the Covert Methods of Entry (CME) team flashed army passes and went to room 220 on the building's first floor which houses branch files. CME teams are trained in lock- picking, safe-cracking, burglary, by-passing alarm systems and unarmed combat.

One of the three-man team punched the branch officer guarding the room in the mouth, put a hood over him and played music to drown out the noise of their activities . The officer was threatened that they'd 'stick him with a syringe' if he caused any trouble. Only one of the team spoke -- he had an English accent. They took a notebook, some files and a few other documents and were out of the building within 16 minutes. Military intelligence sources say the raid and the documents could only have related to Stakeknife.

The CME teams are trained by the Intelligence Corps, based at Ashford in Kent. The Intelligence Corps also runs the ultra-secret counter-intelligence outfit the FRU, the Force Research Unit. It is the FRU -- the intelligence agency which runs Stakeknife as an agent -- which is at the centre of the Stevens Inquiry over claims that it used paramilitary groups as proxy assassination teams. The FRU was headed by Brigadier Gordon Kerr, from Aberdeen. He is now the British embassy's military attachˇ in Beijing.

His unit is supposed to have colluded with the paramilitary Ulster Defence Association in the murder of at least 14 Catholic civilians in Northern Ireland by handing intelligence on republican targets to Brian Nelson, the loyalist group's chief intelligence officer. It subsequently transpired that Nelson, a former soldier in the Black Watch , had infiltrated the UDA for intelligence chiefs in order to facilitate this 'state-sanctioned murder campaign'.

The principal killing that Stevens is investigating is the gunning down in 1989 of solicitor Pat Finucane by loyalists . Former FRU members have co-operated with the Stevens Inquiry in the past about the role the unit played in the murder.

According to FRU sources, Brian Nelson would 'look like a pussycat' compared to the activities of Stakeknife. That's why military intelligence are so desperate to protect him. 'It would be tantamount to being exposed as running a Latin American-style murder squad if the truth came out,' one said. Unlike Nelson, Stakeknife sometimes did the killings himself. He is also supposed to have arranged for republican targets to be in the wrong place at the wrong time so loyalist hit teams could 'take them out'. An intelligence source added: 'This guy was licensed to kill and he killed very many people -- or arranged their deaths.'

The CME team knew exactly what to do to extract all details on Stakeknife from Castlereagh. Until the middle of last week the Special Branch files had been contained in an annexe in the grounds of the police complex. The documents were moved by branch officers to room 220 when workmen arrived last week to start refurbishing the annexe.

The fact that the three-man team knew to go to room 220 immediately implies that there may be some inside knowledge being fed to them from the branch. The men made no attempt to disguise their identities and didn't care that they had to go past CCTV cameras before entering room 220. Either they knew they'd be out of Northern Ireland within a few hours of the job being done or they were aware that none of the CCTV cameras records images on tape -- again this implies inside knowledge. The military passes carried by the men would also have given them clearance to get into the Special Branch section of Castlereagh -- again implying inside help from the police.

One former FRU source said: 'There was no way it was paramilitaries -- they couldn't pull it off. The branch couldn't do it as they'd get spotted by their own pals in the RUC and MI5 just don't do rough stuff like this. There's no one except an intelligence corps CME team who could do this and there is no other motive for them doing it than protecting Stakeknife.'

Although RUC chief constable Sir Ronnie Flanagan says no informers' names were among the documents, intelligence sources claim it's what Flanagan doesn't say that is more telling. 'He doesn't say there was nothing to do with the activities of informers -- and if we are talking about Stakeknife that's crucial,' said one.

An FRU source who used to handle republican informers described Stake knife as a 'vile character', adding: 'If what he was doing came out it would cause massive problems. He'd put the activities of people like Brian Nelson in the shade. He was being directed by the state. He caused the deaths of active republicans and was also allowed to carry on acting as a conventional terrorist -- doing shootings -- with the complicity of his handlers in order to keep his cover.'

Crucially, the FRU's 'east detachment' is based in the so-called 'Green Hut' within the grounds of Castlereagh -- a good source of support and information for the CME team which would have been dropped into Ulster from England shortly before the raid to 'recce' the barracks. Once they'd completed the operation they'd have made their way to a 'clean house' probably on the outskirts of Belfast and headed back to Ashford in Kent, most likely on board a military helicopter from RAF Aldergrove.

This isn't the first time that an army intelligence CME team has tampered with police operations. At the very start of Sir John Stevens' investigations in Ulster -- on January 10, 1990 -- a CME team broke into his Carrickfergus offices and torched the premises. The fire was started at 10.30pm under a table next to a cabinet containing exhibits and statements prepared for the forthcoming arrest of Brian Nelson. The fire alarms had been disabled and telephone lines were dead. A few hours earlier Nelson had fled Northern Ireland on a tip-off from the FRU. FRU whistleblower Martin Ingram (a cover name) says he saw CME specialists celebrating their arson success later in an army bar.

There has even been speculation that some rogue elements within the British Army tried to sabotage Stevens' light aircraft last year. It crash-landed after the undercarriage and air instruments failed in mid-flight -- a situation the manufacturers said was unheard of. An investigation into the incident was hampered when a fire destroyed evidence.

Two separate investigations into the Castlereagh break-in are now under way -- one by the police and one by Sir John Chilcot, a former Whitehall mandarin and an expert on Northern Ireland, who will be assisted by Sir Colin Smith, a former Thames Valley chief constable. Their inquiry will endeavour to find out if rogue security forces were involved. Nuala O'Loan, the Northern Irish police ombudsman, will also launch an investigation if it becomes clear any police officers were involved in the case.

Last night, intelligence sources and former British agents were sure nobody would ever be called to account for 'Branchgate' as the break-in has been dubbed. One could barely conceal his contempt as he described his view of the vow by John Reid, the Ulster secretary, to not rest until he got to the bottom of the 'national security' breach.

'How can this be a breach of national security,' he said, 'when it's obvious that the men who did it are at the very heart of British national security? It leaves you with the feeling that we're living in the biggest sham of a democracy in the world.'

24 March 2002