The man in charge of the army unit that ran Brian Nelson, the British agent behind the killings of several Catholics in Northern Ireland, tried to cover up the extent of the agent's involvement.

Colonel Gordon Kerr, who recruited Nelson to the Force Research Unit (FRU), also defended him to the Stevens Inquiry.

He admitted he had used Nelson to redirect loyalist murder gangs' guns at IRA targets.

But Kerr claimed the plan - far from taking lives - was designed to save them.

'217' lives saved?

Sarah Bynum worked on the Stevens Inquiry from 1989-1991

He said that the FRU informed the Royal Ulster Constabulary of planned UDA targeting and attacks.

In other words, that "Nelson was a prolific provider of life saving intelligence. The statistics of 730 reports about the targeting of 217 individuals are witness to that."

But the Stevens Inquiry refuted this claim early on. Detective Constable Sarah Bynum told Panorama:

"I can't say that it was clear to us that the whole goal of the army having him in place was to save life."

Knowledge denied

Gerald Slane was just one victim of the agent Brian Nelson's targeting.

Gerald Slane's killing was witnessed by his young son

At his inquest, a detective said he was not involved in terrorism.

Colonel Kerr told the Stevens enquiry there was nothing his unit could have done to prevent this murder:

"Slane was killed but no-one in Force Research Unit or Special Branch knew that an imminent attack was being planned, or that he had been singled out as a target."

But Sergeant Benwell, of the Stevens Inquiry, told Panorama:

"That's not correct. They knew that Nelson had been targeting Slane.

"They also knew that he'd been to his intelligence dump and he'd got a photograph of Slane which he'd handed to one of the most prolific killers in the organisation.

Sir John Stevens has been investigating the FRU for three years

"That at least should have set the alarm bells ringing and they should have been passed to the RUC. "

But nothing was passed to the RUC.

And according to Stevens, the Slane case was typical. His inquiry found that the information the army sent to the Special Branch was often incomplete.

'Collusion by omission'

By not taking any action to prevent the events taking their course, this amounted to "collusion by omission", Benwell told Panorama.

Colonel Kerr vehemently denied this, and neither he nor any member of his unit was ever charged.

In the end, just one man took the rap for everyone: Brian Nelson.

'Just not right'

Even though Stevens had already disputed Kerr's claims that Nelson had saved many lives, Kerr made the claim again, while a witness for Nelson's trial in early 1992:

"There were several occasions when targets for assassination were brought to our notice by Brian Nelson... something like 730 reports concerning threats to 217 separate individuals...Threats to life of the individual in all cases"

Nicholas Benwell: incredulous

Benwell was incredulous. "It just wasn't right, it wasn't correct.

"Afterwards I went through all the documents... I could only find maybe two cases where the information given by Nelson may have been helpful to the Security Forces in preventing attacks."

It may not have been true. But the judge, in his summing up, said:

"I give, of course, considerable weight to the fact that he passed on what was possibly life-saving information in respect of 217 threatened individuals."

Nelson was given a ten-year sentence which, considering what he had done, was lenient by any standard.

Questionable claims

Some other claims made by the Colonel have also been questioned.

Kerr told Nelson's trial: "I firmly believe that the purpose of running agents is not only to prevent terrorist killings, but also to bring about the arrest of terrorists."

Asked if Nelson's activities had led to terrorists being arrested or guns recovered, Benwell told Panorama:

"I cannot think of one occasion where the information provided by Nelson led to any of the activities you describe."

So what did the state get out of Mr Nelson?

Benwell said: "You may well ask."