The question of how far a state should authorise its agents to go in seeking and using secret intelligence is one of the big unresolved issues of public policy for democracies today. The tension between security and privacy sits at the heart of broader debates concerning the relationship between the citizen and the state. The public needs-and wants-protection from the very serious threats posed by domestic and international terrorism, from serious criminality, to be safe in using cyberspace, and to have active foreign and aid policies to help resolve outstanding international problems. Secret intelligence is widely accepted to be essential to these tasks, and to be a legitimate function of the nation state, yet the historical record is that it also can pose significant ethical risks.