What are the links between the UK and US security services?
Evidence continues to emerge about the CIA's secret detention and interrogation programme.
And now calls grow on this side of the Atlantic for an inquiry into claims that Britain colluded in the torture of terror suspects.
Stephen Grey investigates the relationship between the US and the UK security services in the hidden and continuing War on Terror.
And he asks what did the UK Government know about "rendition flights."
To learn more listen to File on 4, 2000 BST, Radio 4, Tuesday 28 July 2009.