How far should the state look into our lives, and what should be done with the information that is collected? Computers now contain millions of records and intelligence files; the police and security services have a formidable range of surveillance devices, from simple phone-tapping equipment to advanced laser-bugs. Tom Mangold continues his report on security by examining the state's intrusion into the lives of British citizens, and asks if better safeguards are needed against the services who carry it out.