THE closed and secretive world of Irish republicanism was thrown into turmoil last night after one of Gerry Adams’s most trusted lieutenants admitted that he had been a British agent for 20 years.

Denis Donaldson, who was acquitted last week of charges of leading an IRA spy ring in the “Stormontgate” affair that ended Northern Ireland’s power-sharing executive three years ago, was a member of Belfast’s republican elite, whose credentials in the fight to end British rule in Ireland would, until now, have been regarded as unimpeachable.

But after he was “outed” yesterday and thrown out of Sinn Fein by Mr Adams, who shared a cell block with him during the 1970s when Mr Donaldson, 55, was welcomed into the inner sanctum of “Young Turks” who took control of the republican movement, the question raised in West Belfast was: “If Denis, then who else?” Mr Donaldson’s extraordinary confession came a week after he and two other men, including his son-in-law, were sensationally acquitted of charges of possession of sensitive security documents, which resulted in the forced rehousing of 2,000 people at a cost of £300 million.

In one remarkable — and, for Mr Donaldson, extremely lucky — respect, his expulsion from Sinn Fein, the political wing of the Provisional IRA, also marks a significant departure from the traditional fate of a republican charged by his or her own comrades of “working for the Brits”.

It is not unreasonable to suggest that only six months ago, prior to the IRA’s statement that it was ending its armed campaign to end British rule in the north of Ireland, Mr Donaldson would have suffered the fate of scores of earlier “volunteers” condemned to death for spying and been shot through the back of the head, his hooded body left on a roadside.

At a press conference in Dublin, Mr Adams said that Mr Donaldson had admitted to being a paid British agent for the past 20 years. Last night Mr Donaldson said that he deeply regretted his activities, adding: “I was recruited in the 1980s after compromising myself during a vulnerable time in my life. Since then I have worked for British intelligence and the RUC/PSNI Special Branch.”

According to Mr Adams, Mr Donaldson had approached Declan Kerney, the party’s Northern chairman, after being warned by police that he was going to be exposed and that his life was in danger. At a subsequent meeting with Mr Kerney and Leo Green, another Sinn Fein official, he admitted to being a British agent and was expelled from the party.

Asked if he suspected that there had been an informer, Mr Adams said: “I was very, very suspicious and some of us were very suspicious when the events of 2002 unfolded, when we saw this hugely orchestrated operation at Stormont, because we knew there was no Sinn Fein spy ring at Stormont.”

Only a week ago Mr Adams appeared shoulder to shoulder with Mr Donaldson outside Stormont after the spying charges were dropped by the Director of Public Prosecutions “in the public interest”. The case was heard at an unlisted hearing at Belfast Crown Court as the Queen and Prince Philip made a visit to the city, prompting charges that the timing was not coincidental. Unionists have demanded that the “public interest” in dropping the charges be explained.

It is likely that yesterday’s developments may go some way to explaining what seemed, even by Northern Ireland’s standards, a murky decision.

Mr Adams sought to divert attention from the news that his movement was penetrated at the highest level by blaming “securocrats” and the British Government for “political policing” that damaged the institutions of the Good Friday Agreement. “The fact is that the collapse of the political institutions was a direct result of the actions of some of those who run the intelligence and policing system of the British,” he said. “The fact is that the key person at the centre of those events was a Sinn Fein member who was a British agent. This is entirely the responsibility of the British Government.

“If Britain’s war is over then the British Prime Minister needs to come to terms with the fact that he has to end the activities of the securocrats.”

A Police Service of Northern Ireland spokesman said: “Police do not confirm or deny whether an individual is or was an informant.”

Unionists were astonished by the expulsion. The Democratic Unionist MP Jeffrey Donaldson said: “This has certainly given an added twist to the entire Stormontgate scandal and confirms our view that the reasons the court decided not to prosecute was because to do so would have compromised an agent of the state and sensitive security documents. It raises the question that the decision not to proceed was politically motivated.”

William Mackessy, one of the three men cleared of the spying charges, once worked as a security guard in the offices of Sir Reg Empey, then a minister in the powersharing executive at Stormont. Sir Reg, now leader of the Ulster Unionist Party, said that he would be seeking an urgent meeting with government officials.

Sir Alasdair Fraser, Northern Ireland’s Director of Public Prosecutions, declined to comment. But Sir Reg said: “If this was the person who was being protected by the DPP, then there is no reason why these prosecutions cannot proceed. It actually debunks the claims by Sinn Fein there was no spy ring operating inside Stormont, when in fact there was.”

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