The agent — codenamed Stakeknife — is understood to have been taken to a safe house. The dramatic move brings to an end a 30-year career during which he penetrated the highest ranks of the IRA. He was moved because his exposure would have led to near-certain kidnap, interrogation and murder by the terrorist organisation.

Defence sources confirmed last night that Stakeknife was being taken to a safe location. The military acted after receiving intelligence that the agent’s name was about to be published in Irish and Scottish newspapers.

Stakeknife’s card has been marked since Sir John Stevens, the commissioner of the Metropolitan police, revealed last month that he intended to question him as part of a long-running inquiry into alleged collusion by the security forces in paramilitary killings.

“We will be questioning Stakeknife soon. We fear other informants have been sacrificed to save him and we will be asking him about that,” Stevens said.

Stakeknife, whose existence was revealed by The Sunday Times four years ago, was regarded by the British military as “the jewel in the crown” of its network of agents in Ireland.

He first volunteered to work for the army in the 1970s and was steered to an influential position in the IRA.

He was run by members of the army’s Force Research Unit (FRU), the same intelligence organisation which is at the centre of Stevens’s inquiry. Stakeknife was paid about £60,000 a year for his services and his intelligence was read at cabinet level.

Now in his sixties, Stakeknife is originally from Belfast but was living in Dublin until yesterday’s security alert. He spoke to The Sunday Times more than a year ago, saying he had had to cut down his involvement in the IRA for health reasons and that he might tell his story when he had recovered.

The Sunday Tribune in Ireland and Sunday Herald in Scotland both name Stakeknife today and outline his role within the IRA. If he decided to talk now that his identity has been revealed his story would be political dynamite. Stevens — who has forwarded files on FRU soldiers to Northern Ireland’s director of public prosecutions — suspects Stakeknife and his handlers are linked to up to 40 preventable murders.

Stakeknife was recently advised by the army to move to the republic so he would be outside Stevens’s jurisdiction.

The army is furious with Stevens. Stakeknife’s handlers claim that he was responsible for saving far more lives than he ever cost. They point out that Britain was effectively at war with the IRA and in such circumstances their tactics were necessary.

Stakeknife’s handling was one of the army’s most sensitive secrets. An FRU unit, with its own fleet of vehicles, was maintained at the army’s Northern Ireland headquarters in Lisburn to handle him.

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