Part of the Secret Britain series.
Peter Taylor meets people who have kept state secrets.
As part of Radio 4's Secret Britain series, Peter Taylor meets people who keep or have kept the darkest state secrets, to hear how it feels to live a life in the shadows:
The Derry family who put their lives on the line for peace; the Muslim agent who spies on Islamist extremists; the mandarin charged with guarding Britain's secrets; and the Special Branch officer who infiltrated subversive revolutionary groups.
Presenter: Peter Taylor
Producer: Richard Knight.