For the first time in its 115-year history, MI5 is pulling back the curtain on its shadowy past. A new exhibition at the National Archives in London, MI5: Official Secrets, offers the public an
unprecedented look at Britain's domestic spy agency, showcasing everything from double agents and Cold War betrayals to real-life spy gadgets.
Among the stories on display is that of Karl Muller, a suspected German spy captured in 1915. What led to his downfall? A lemon. Found in his coat, Muller claimed he used it to clean his teeth. In reality, he’d used its juice as invisible ink to report British troop movements. MI5 intercepted the letter, and Muller was later executed at the Tower of London.
The exhibition traces MI5’s origins from its founding in the early 1900s—amid fears of a German invasion—under its first chief, Vernon Kell. Today, the agency employs over 5,000 people and works closely with its foreign counterpart, MI6, made famous by the James Bond films.
“Real MI5 work is very different from the fiction,” said MI5 Director Ken McCallum at a preview event. “It’s ordinary people doing extraordinary things to keep the country safe.”
The show also explores the agency’s darker chapters. One Cold War exhibit features a briefcase and passport left behind by Guy Burgess, a British diplomat-turned-Russian spy who defected to Moscow in 1951. Another includes a note confirming Queen Elizabeth II was told in the 1970s that her art advisor, Anthony Blunt, was a Soviet agent. Her reaction? Calm and unsurprised.
More recent artifacts include a mortar shell fired by the IRA into the garden of 10 Downing Street in 1991.
The exhibition also highlights the evolving face of MI5. In 2022, women made up nearly half the agency’s workforce. The idea isn’t new—legendary agent Maxwell Knight suggested back in the 1930s that “a woman’s intuition is sometimes amazingly helpful.”
Interactive elements invite visitors to test their spy potential, including memory and code-breaking challenges.
The MI5: Official Secrets exhibition is free to attend and runs until September 28.
Photo by Security Service, Wikimedia commons.