Brian Nelson, the former British army agent at the centre of alleged security force collusion with loyalist paramilitaries in Northern Ireland, has died.
Brian Nelson operated as the intelligence chief of the UDA
It is believed he had a brain haemorrhage two weeks after suffering a heart attack. BBC News Online looks at his controversial past.
Nelson, who operated as the intelligence chief of the Ulster Defence Association (UDA), was recruited by British military intelligence at the height of the Troubles.
His death came just days ahead of a report focusing on his part in alleged collusion between loyalist paramilitaries and the security forces.
Metropolitan Police Commissioner Sir John Stevens is set to publish his findings on the murder of solicitor Pat Finucane on Thursday.
Nelson provided a dossier on the lawyer to the UDA who murdered Mr Finucane in February 1989.
Originally from Belfast's Shankill Road, he is said to have provided the vital intelligence that guided killers to their targets.
The leading loyalist was recruited by Colonel Gordon Kerr to the Force Research Unit (FRU) - an Army agency involved in gathering intelligence from loyalists.
Brigadier Kerr, who is now military attache in Beijing, also defended Nelson to the first Stevens Inquiry.
In February, Sir John said he was preparing prosecution papers surrounding the brigadier.
Sir John stopped short of saying that he was recommending a prosecution.
He said that would be a matter for the Director of Public Prosecutions in Belfast.
Nelson, a former soldier, was living at a secret location in England under an assumed name.
His role as an Army agent was discovered in 1990 and he was jailed for 10 years on five counts of conspiracy to murder.
At his 1992 trial, Brigadier Kerr said Nelson's work had "saved many lives".
He said at the time: "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."
However, in June last year,
BBC's Panorama programme alleged Brigadier Kerr tried to cover up the extent of Nelson's involvement in the murders of Catholics.
He admitted he had used Nelson to redirect loyalist murder gangs' guns at IRA targets.
It is understood that Sir John has passed on files on at least 20 members of the security forces, both serving and retired, to the Director of Public Prosecutions.
Sinn Fein has said Nelson's death reinforced calls for a public inquiry into the murder of Pat Finucane.
Senior member Alex Maskey said Nelson had been "central to the British policy of collusion and had played a central role in the murder of the Belfast solicitor".
"Many of those publicly identified as playing a role in that killing have themselves now died," he said.
"But the questions for the British Government will remain until the truth behind collusion is uncovered."
A heavy smoker, Nelson had suffered from heart trouble for several years.
He learned six months ago he was suffering from
cancer, according to friends.