The Troubles: A Secret History Episode Rating Graph

At the end of the Seventies, the IRA built its own internal security system to root out informers. But British intelligence found a fatal flaw that unlocked many of the IRA’s secrets.

Unionist anger grew as IRA attacks on the security forces killed members of their community. When Margaret Thatcher signed the Anglo-Irish Agreement in 1985, giving the Republic of Ireland political influence in the North, the anger spilled over leading to loyalist groups rearming. Using intelligence leaks to boost their campaign of killing, new information reveals MI5 agents operating inside the largest loyalist group, the Ulster Defence Association.

An investigation into the murders of two young brothers uncovers secrets from the loyalist gang that carried out the attack.

The inside story of how the Troubles ended told by those who fought the IRA's war and by those at the heart of peace efforts.

A behind-the-scenes look at how investigative journalists in Northern Ireland track down stories, uncover secret papers and persuade people to speak out.