But it is far from the first time the loyalist killing machine has had agents in key positions.

In the early 1980s leading racketeer Jim Craig was passing on UDA secrets not just to the RUC, but also the IRA, in order to feather his nest. He was gunned down by his former comrades just months after setting up UDA leader John McMichael to be murdered in an IRA car bomb attack in 1987. But the most notorious loyalist informer was FRU agent Brian Nelson, who was allowed to plot dozens of terrorist attacks before his involvement in the 1989 murder of solicitor Pat Finucane triggered the Stevens inquiry.

A number of other leading UDA figures involved in the Finucane murder have also been named as informants, including the terror group's quartermaster William Stobie - who was later murdered by his former 'comrades'.

Ken Barrett, the only man to be jailed for the murder, was later exposed as an RUC informant and Tommy 'Tucker' Lyttle was branded a tout after his death.

It was not just the UDA that was infiltrated by the security forces. A number of very prominent UVF figures are believed to be informants. Mount Vernon UVF leader Mark Haddock was exposed as a double agent who had been involved in a string of murders.

The republican movement has also been littered with informants, including Freddie 'Stakeknife' Scappaticci, Eamon Collins, Martin McGartland and murdered Sinn Fein official Denis Donaldson.