Give Me a Crash Course In . . . Stakeknife

Who is Stakeknife? Stakeknife – or Steak Knife – is the most senior IRA figure so far outed as having worked for British intelligence. He is alleged to be Freddie Scappaticci, a former IRA member who now lives abroad. Scappaticci has consistently denied that he was a British spy.

Why is Scappaticci in the news? The Northern Ireland Director of Public Prosecutions, Barra McGrory, announced this week that he has asked the chief constable of the PSNI, George Hamilton, to investigate allegations that Scappaticci was involved in at least 24 murders. It is speculated that he could be responsible for up to 40, some of his victims allegedly sacrificed to protect his identity. McGrory also wants Hamilton to investigate the British security-service controllers who handled him.

How senior was Scappaticci? Very senior. He was interned in the early 1970s with, among others, Gerry Adams. From an Italian immigrant family and originally from the Markets area of Belfast, he is now in his late 60s and living in hiding under security-service protection. A trusted figure among republican leaders, he rose during the 1970s and 1980s to become head of the IRA's internal-security department, its so-called nutting squad.

What did it do? It vetted and debriefed IRA members and hunted out suspected informers. It was a feared unit, with Scappaticci viewed as "judge, jury and executioner". The former IRA man Eamon Collins, himself killed by the IRA, was briefly a member of the squad. In his book Killing Rage he characterised Scappaticci as a cold-hearted killer. Collins described him well as "small and barrel-chested with classic Mediterranean looks – olive-skinned with tight black curly hair".

What else did he say about Scappaticci? Collins told one particularly chilling story. He wrote that he asked Scappaticci, whom he called Scap, and another senior nutting-squad figure, John Joe, whether they told their victims that they were about to be killed. Collins wrote that Scappaticci "turned to John Joe and started joking about one informer who had confessed after being offered an amnesty. Scap told the man that he would take him home, reassuring him that he had nothing to worry about. Scap had told him to keep the blindfold on for security reasons as they walked away from the car. 'It was funny,' he said, 'watching the bastard stumbling and falling, asking me as he felt his way along the railings and walls, "Is this my house now?" and I'd say, "No, not yet, walk on some more . . . " ' . . . and then you shot the f**ker in the back of the head,' said John Joe, and both of them burst out laughing."

Why did Scappaticci become an agent? In 1978, reportedly, he was viciously beaten by a fellow high-ranking member of the Provisional IRA, an event said to have prompted him to offer his services to the British security services; he eventually came under the control of the British army's shadowy "force research unit".

Was Stakeknife well remunerated? A figure of £80,000 a year has been mentioned, although Scappaticci has denied this.

When was Scappaticci exposed? He was named as an agent in 2003. Initially he denied the charge, but he then fled Belfast. The media is not allowed to report anything that could suggest where he is living or to show images of what he now looks like.

Will these investigations lead anywhere? Establishing the truth of the "dirty war" has proved very difficult, but let's wait and see. It would be fascinating were he to give evidence and be cross-examined in any murder trial or trials. He has many dark stories to tell. He is also known to dislike Deputy First Minister Martin McGuinness, of Sinn Féin. In 1993 The Cook Report, on ITV, secretly recorded him alleging that McGuinness was a senior IRA figure. It could also be embarrassing for the British security services, which are alleged to have allowed murders to be committed to protect their "crown jewel" agent. These security figures may contend that as an agent he saved many lives. Certainly the families of his alleged victims are desperate to hear the truth about Stakeknife.