An undercover British intelligence officer has lifted the lid on one of the murkiest episodes of Britain's secret war against the IRA to reveal that a British agent conspired with loyalist paramilitaries to murder republicans.
The man, known only as 'Geoff', is the first agent handler to break the official silence surrounding allegations that Britain has waged a 'dirty war' against IRA sympathisers. The officer's story, to be aired on the BBC2 programme Brits this week, reveals that Brian Nelson, a British agent who infiltrated the loyalist paramilitary Ulster Defence Association (UDA), was officially assisted by British intelligence to help UDA killers murder republicans.
Working as information chief for the UDA, Nelson was encouraged by the secret army unit he worked for - the Force Research Unit (FRU) - to pass on intelligence to Loyalist killers, so that they could track down their victims.
Remarkably, some of the intelligence was provided by the FRU itself. In his interview Geoff admits that Nelson 'strayed outside the law at our behest'.
Nelson was meant to save lives by passing details of planned 'hits' to his handlers, who were supposed to pass it on so the operation could be thwarted. However, it did not always work like that. The killing of Gerard Slane on 22 September 1988 illustrates the murderous mess the FRU and its agents got into.
Just after 4am, four masked gunman from the Ulster Freedom Fighters (UFF), the UDA's killer wing, sledge-hammered their way into the Slane's house off the Falls Road, and shot him four times in the head. They claimed that he had been involved in the killing of one of their own a fortnight earlier. An RUC detective said there was nothing to suggest that he had.
Brian Nelson had provided the UFF with the detailed intelligence that had enabled the 'hit' to go ahead. He had found Slane's address, checked it in the electoral register, got hold of a photograph and made out a personal file on him - all with the blessing of the FRU.
'Brian Nelson may not have pulled the trigger,' Slane's widow, Teresa says, 'but to me he was as guilty of my hus band's murder as the actual murderers themselves.' Nelson told his handlers about the plan but the information was not acted upon.
Nelson was unmasked as an army agent involved in murder in 1990 after John Stevens, then the Deputy Chief Constable of Cambridgeshire, investigated collusion between the security forces and the loyalist paramilitaries. Nelson pleaded guilty on five counts of conspiracy to murder - Gerard Slane was one - and sentenced to 10 years.
These charges were only the tip of an iceberg of conspiracy and killing that involved Nelson, the FRU and British intelligence from the early 1980s onwards.
Nelson rose to become the UDA's intelligence chief for the whole of the province. His orders from the FRU were to encourage the UFF to stop killing innocent Catholics and concentrate its murderous energies on targeting suspected republican terrorists. He became involved in even more controversial killings, most prominently that of the lawyer, Pat Finucane. This remain one of the matters still under investigation by John Stevens, who is now Commissioner of the Metropolitan Police.
The final part of Peter Taylor's series, Brits , will be shown on BBC2 on Wednesday 31 May at 9.30 pm.