How do we balance our belief in human freedom with the need to defend ourselves against those who believe the use of terror can be justified? Can our handling of security risk and the laws we pass to deal with them distort our response to the threat of terrorism? In this sobering and remarkably frank analysis based on her 2011 Reith Lectures, Eliza Manningham-Buller, ex-Director General of MI5, the British Security Service, talks about key events during her tenure - from the threat of the IRA to al-Qaeda. She states that torture works but must never be used, how intelligence is gathered and why surveillance is necessary to protect democracy, the importance of the rule of law and why without security there can be no liberty.