The Cambridge Five are perhaps the most infamous spy ring of the 20th century. They worked their way into the upper ranks of British Intelligence in order to spy for the Soviets, betraying their country and causing the deaths of dozens of British agents. So why were none of them ever prosecuted? How did they get away with it? In this episode, we use the intelligence records in our archives to illuminate three stories of double agents. Mata Hari was executed for using her seductive powers to spy for the Germans, but where’s the evidence that she was actually a spy? Did the Cambridge Five get a pass because of their elite social status? How did British laws against homosexuality make their own agents vulnerable to Soviet blackmail? These questions and more are answered in the final instalment of our mini-series on spies and espionage in British history.