Raymond White was the head of RUC Special Branch that ran informers in the IRA

Although it has long been known that the IRA was riddled with agents and informers – including many close to Gerry Adams – last night BBC Spotlight broadcast a series of revelations which point to the extraordinary scale of that counter-terrorist operation.

In 2002, the IRA broke into RUC special branch headquarters in Castlereagh and stole documents containing the code names of the agents within the IRA in Belfast.

Sir John Chilcott, the former permanent secretary of the Northern Ireland Office, told the programme that despite having gone to such effort to obtain the information, it was “never put to use”. He asked: “Was that actually because it was too hot to handle by them for the Provisional leadership?”

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Spotlight said that security and republican sources had told it that the Castlereagh break-in exposed so many agents that it “posed an impossible question: How could they kill them all?”.

Raymond White, the former head of RUC Special Branch, said that agents had been able to help steer the IRA towards politics.

Former IRA director of intelligence Kieran Conway said that the security agencies’ war against the IRA had broken it.

He said: “The attrition rate was just so appalling.

“The SAS, the British intelligence services were obviously in a position to intercept most operations.

“It was absolutely clear that we were losing if we hadn’t already lost the war and that it was time to cash in the chips.”

Mr White said that agents of influence within the IRA and republican movement had been used to push political ideas and also “raised suspicions about the abilities of certain people, and that brought about change”.

He said that “the intelligence world played an immense part in bringing about, shall we say, a realisation within the Provisional IRA that they had passed the post in terms of the armed conflict”.

When asked if the security agencies wanted the army council to remain intact because of how infiltrated senior IRA figures and those around them were, he said: “The army council was made up of people of, shall we say, varying abilities and varying influence and once you knew those abilities and influences then obviously those that sort of moved in their midst or attended to their needs or were able to sort of make commentary in their presence – all those things had a collective influence ... over a period of time.”

The senior intelligence figure said that he had personally asked the then prime minister Margaret Thatcher about the legal grey zone in which they were operating with informers whereby the police were telling them to act as normal terrorists so as to not arouse suspicion, while continuing to feed information through to their handlers.

He said that the essence of Mrs Thatcher’s response was to “carry on doing what you’re doing, but don’t get yourself caught”.

Spotlight also said that it had obtained John Stalker’s 1980s report into alleged ‘shoot to kill’, and a follow-up report by another officer – secret reports which have not been published.

The programme said it was “easy to see why they’ve been kept secret for so long” because they showed “a massive cover-up by the guardians of the law, one in which police officers were instructed to lie to detectives and prosecutors and in which senior police and MI5 officers destroyed evidence, all in the name of protecting an informer and other intelligence sources”.

Spotlight said that the reports recommended prosecution of police and MI5 officers but it was decided that pursuing those cases in court would run contrary to the interests of national security.

The programme was the fourth instalment of Spotlight On The Troubles: A Secret History.