Who authorised the torture of terror suspects in US custody?

The official line out of George W Bush's White House was that torture did not happen on America's watch.

In Licence to Torture, Panorama looks behind the Bush government's line and finds a paper trail that questions the validity of that assertion.

Previously classified papers released in Washington reveal both the path taken by the Department of Defense and intelligence agencies as they searched for interrogation techniques to employ in order to get information from al-Qaeda suspects, and the legal arguments used to validate them.

One of those techniques was waterboarding, which has since been classified as torture in breach of both US and international law.

Reporter Hilary Andersson finds that debate over what was - or was not - legal when it came to interrogation, has permeated mainstream America.