When Freddie Scappaticci, a stocky, second-generation Belfast Italian, surfaced in his solicitor’s office last week, he had the cuddly paunch and grizzled curls of a Mediterranean grandpa — but his puffy eyes were those of a man on the edge of a breakdown.

As well they might: he had been outed in the press as Stakeknife, the jewel in the crown of British military intelligence in Northern Ireland, an allegation he denies but which I pursued from the early 1980s until finally learning his name four years ago.

The evidence against him is sufficient for Sir John Stevens, the London police commissioner, who heads the long-running official investigation into collusion between the security forces and loyalist paramilitaries in Northern Ireland, to want to interview him.

The unmasking of Stakeknife marks a seismic moment in the Northern Ireland process: the beginning of the end for both the IRA and the Force Research Unit (FRU), the controversial British Army undercover unit that handled him.

The IRA leadership is thoroughly discredited for trusting him for so long; all their talk of secrecy and security is exposed as a sham. And on the army’s part, all the FRU’s embarrassing secrets are likely to come tumbling out under the spotlight of the media and the Stevens inquiry.

His unmasking is also the trigger for some disturbing questions. Within the IRA, Stakeknife had the task of rooting out informers in the ranks. The IRA must ask itself if any of its volunteers were wrongly killed with the connivance of the British — and the army itself must ask if others could have been saved.

But who is Scappaticci? Are his denials to be believed? I have had nearly 20 years to mull over this extraordinary enigma.

I FIRST heard the codename Stakeknife in the early 1980s, when an informant told me that he was the army’s top agent within the IRA. He was not part of the political leadership, my source said, but was a hard-line military figure whose identity “you would never guess at”. And he had such a stunning overview of the organisation that a whole British intelligence unit was devoted to handling him.

His output was so prolific that two handlers and four collators worked full-time on his leads. His source reports were read by ministers. Army careers were built on his information.

I wrote about Stakeknife — or “Steak Knife” as I assumed it was spelt — in the Northern Ireland newspaper I worked for at the time, and occasionally I dropped the codename into conversations at military and police gatherings to test the reaction.

Generally I got funny looks and raised eyebrows, but occasionally there were nuggets of information. A handler was mentioned, and I learnt that Stakeknife was from Belfast and had been recruited in the 1970s.

But who was he? Time gradually narrowed the field: by the late 1990s, death, retirement and imprisonment had taken its toll on the 1970s IRA leadership. Fewer and fewer people fitted the Stakeknife profile I had built up.

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