Willie Carlin - Former Spy

The long and bloody conflict in Northern Ireland was known euphemistically as The Troubles, while one aspect of it got a separate label, The Dirty War. That was the name given to the covert operations of the British state – both army and intelligence - infiltrating the IRA, running informers and agents to undermine the republican movement from within. Stephen Sackur interviews one of those agents, Willie Carlin, who became an undercover spy within the political wing of the IRA. He’s written a book exposing his secrets. How does he justify what he did?