MI5: From Secret Service Bureau to Modern Security Agency

This chapter explores the evolution and functions of MI5, the British military intelligence agency, from its origins in the Secret Service Bureau to its role in protecting democracy, countering terrorism, and espionage within the UK. It compares MI5 to MI6, highlighting their respective roles in security and foreign intelligence and delves into the history of various UK military intelligence services during World War II. The chapter discusses the challenges of assessing MI5's success due to its secretive nature, historical incidents like espionage cases, and the evolving threats faced during the Cold War era and post the Cold War reforms.