MI5

In this episode, we focus on MI5, the United Kingdom’s domestic counter-intelligence and security agency, tracing its origins from its 1909 creation to counter German espionage through its evolving role in confronting Cold War subversion, international terrorism, and state-sponsored threats from countries such as Russia and China. The episode explores landmark moments in MI5’s history, including the Double-Cross System of World War II and the Portland Spy Ring investigation, while also examining the agency’s structure, legal oversight, accountability mechanisms, and controversies around surveillance and informant handling. It also highlights how MI5 continues to adapt its intelligence tradecraft to emerging technological risks and works closely with police, government partners, and international allies to protect national security.