Will Ulster's dirty war claim one of Britain's most senior soldiers?

Finucane Inquiry: Director of Public Prosecutions considers charges against six security force members over loyalist murders of Catholics

When Brian Nelson, a double agent who played a leading role in the killings of dozens of republican suspects, stood trial in 1992 for conspiracy to murder he had surprising support from a surprising quarter: a senior Army officer.

Colonel Gordon Kerr, the commander of a shadowy Army intelligence unit, testified that his agent, far from being involved in murder, had saved lives by giving information about 730 threats to 217 people. Despite the evidence, Nelson was jailed for 10 years on five counts of conspiracy to murder.

But the link between Nelson and Colonel Kerr, who has since been promoted to brigadier and is the military attaché in Beijing, is central to Britain's longest criminal investigation, started 14 years ago. Today, the Metropolitan Police Commissioner, Sir John Stevens, publishes the main findings of his investigation into collusion between security forces and the Protestant paramilitaries.

Most of the 3,000-page report is likely to remain secret, but the inquiry has uncovered evidence of a dirty war in which a covert Army unit passed details of suspected IRA members to loyalist death squads to murder them in the 1980s and 1990s. Among those killed as a result was Pat Finucane, a Belfast solicitor shot in front of his wife and family in 1989. The unit in the scandal is Colonel Kerr's Force Research Unit (FRU). Sir John and his detectives have concluded through three inquiries that it was "running out of control" and four or five members "ignored the rule of law" and operated by their own rules.

Colonel Kerr was aware of the type of operations his men carried out, Sir John's detectives said. Evidence against him and up to six others is with the Crown Prosecution Service to decide if charges, including conspiracy to murder, should be brought. Sir John also uncovered widespread collusion between the RUC Special Branch, who were responsible for running agents, and loyalist paramilitaries, which went unchecked for years. His believes the renegade Army officers approved the murder of Mr Finucane because of his suspected links with the IRA, although the inquiries have found no evidence to support claims that he was involved.

The FRU passed information to loyalist terrorists, mainly through Nelson, an agent the unit recruited who infiltrated the Ulster Defence Association. He may have been linked to more than 30 murders. Many victims had no involvement with terrorism: in one case, the gunmen killed the innocent brother of a man suspected of being an IRA terrorist. Last week Nelson died but the cause has yet to be officially established.

Sir John, who was plain "Mr" and deputy chief constable of Cambridgeshire at the time, began inquiries in September 1989, after an investigation by John Stalker, the former deputy chief constable of Greater Manchester, into claims of an official Army "shoot-to-kill" policy. Mr Stalker's inquiry was abandoned in May 1986 after he was wrongly accused of corruption and disciplinary offences.

The first inquiry, ordered by Sir Hugh Annesley, then the RUC's chief constable, was caused by the murder of a Catholic. Loughlin Maginn had been shot and the loyalist death squad responsible, the Ulster Defence Association, said he was an IRA intelligence officer. Mr Maginn's family said he had no terrorist connections. But the UDA published a police intelligence document videoed by soldiers sympathetic to them and leaked. They also posted other leaked security force documents in an attempt to prove the accuracy of their targeting.

This triggered a diplomatic furore. What the Stevens team did not know then was that Nelson had provided the video camera that sealed Maginn's fate. This was part of a pattern of collusion unearthed by the Stevens inquiries. As UDA chief intelligence officer, Nelson compiled dossiers on targets for assassination, including information on Finucane. Despite claims from Colonel Kerr that Nelson had saved many lives, the Stevens inquiry has found evidence of only two murders he prevented, one of which was an attempt on Gerry Adams, the Sinn Fein president.

The Stevens inquiries were hindered by the FRU and RUC special branch. The report today concludes the Army burnt the headquarters of his inquiry team in 1990. Sir John believes FRU officers firebombed his base at Seapark, Carrickfergus, destroying everything inside. Fortunately, they had copied vital documents.

The inquiry decided neither ministers nor senior officers knew what was happening, but it attacks the lack of control on intelligence operations. The Finucane family and supporters, including Sinn Fein, think his murder was part of a high-level conspiracy and have no faith in Sir John.

A public inquiry into the issue looks increasingly inevitable and Peter Cory, a retired Canadian judge who has been asked by the Government to investigate the Finucane murder and others, is expected to recommend that.

The Collusion Inquiries

February 1989 Pat Finucane, a solicitor who represented leading republicans, is killed.

September 1989 John Stevens, who was deputy chief constable of Cambridgeshire, secures 48 convictions, after his first inquiry into security breaches.

10 January 1990 Army suspected of arson attack on Stevens inquiry papers.

April 1993 Second Stevens inquiry starts into matters resulting from first inquiry.

april 1999 Third Stevens inquiry begins into collusion claims between security forces and loyalist paramilitaries, and murder of Finucane.

December 2001 William Stobie, the only man charged over the Finucane murder, shot by loyalists after the case against him collapsed.

April 2003 Brian Nelson, the army agent who helped UDA killers identify republican targets, dies.

17 April 2003 Sir John Stevens issues recommendations from inquiry.

End of 2003 Inquiry concludes.