Stakeknife - The Spy in the IRA (2017) BBC

In the Northern Irish conflict spying was a very dangerous game, through recordings obtained by Panorama the IRA’s chief interrogator explains how he extracted information from informers before they were shot. This may seem typical given the circumstances of war except that for years the interrogator himself was one of Britain’s most important spies. Codenamed Stakeknife, he was unmasked in 2003 as Freddie Scappaticci, he rose through the ranks of the IRA to run their internal security unit but now Stakeknife and his spy masters are the subject of a major criminal inquiry. This Panorama special investigates if fellow spies sacrificed so he could continue to spy himself? Over the course of Panoramas investigation they uncovered classified reports that link Scappatici to at least 18 murders. Some of these victims were themselves agents and informers and now a new £35 million criminal enquiry has been launched to get to the bottom of it.