He was an intelligence chief of the Ulster Defence Association (UDA), and also a clandestine agent for the British Army's Force Research Unit during the conflict.

[2] In the early 1990s, following the murder of Loughlin Maginn, John Stevens was named to investigate allegations of collusion between loyalist paramilitaries and the Royal Ulster Constabulary (RUC).

Stevens spoke to John Deverell, head of MI5 in Belfast, who confirmed that Nelson had worked for Army Intelligence and not the RUC.

Sharp disagreements developed between the two security branches as the extent of Nelson's illegal activities within the Force Research Unit (FRU) was uncovered.

Using information that should have been confidential to his handlers, he produced dossiers or "Intelligence Packages" including backgrounds, addresses, photos and movements on proposed targets, which were passed on to UDA assassins.

Kerr claimed that Nelson had warned the Intelligence Corps of more than 200 murder plots by loyalist death squads, including one which targeted Sinn Féin leader Gerry Adams.

[2] Nelson claimed that in 1989 he had warned his handlers of UDA plans to murder solicitor Pat Finucane, who had been successfully representing IRA suspects in court.

One allegation was that, following a tip off from Nelson, the Intelligence Corps kept secret a plot to murder Paddy McGrory, a solicitor representing the families of the Gibraltar Three.

[16] Nelson was accused of setting up the killing of republican sympathiser, Francisco Notarantonio, aged 66, to divert the UDA away from wrongly targeting "Stakeknife", Frederico Scappatici, a senior IRA member and informer for the "shadowy" FRU, the army intelligence unit.

Loyalist Sam McCrory killed retired taxi driver and father of eleven children, Notarantonio, who had been interned in 1971.