Britain’s domestic intelligence agency has granted unprecedented access to its private collection of espionage equipment and historical items for a major new exhibition at The National Archives.

Set to open on 5 April at the Kew facility in London, “MI5: Official Secrets” marks the first time in the agency’s 115-year history that it has collaborated on a public exhibition exploring its secretive past.

Among the never-before-seen items is a leather briefcase abandoned by Cambridge spy Guy Burgess at the Reform Club in London before his defection to the Soviet Union in May 1951. The case, containing letters, papers and photographs, was later confiscated by MI5 after fellow spy Anthony Blunt removed incriminating evidence from a separate briefcase Burgess had left behind. Visitors will also be able to view Burgess’ British passport for the first time.

Sir Ken McCallum, Director General of MI5, said: “We are pleased to be able to loan these items to The National Archives for this groundbreaking exhibition. Sharing unique items from our own collection brings to life – in tangible form – some of how MI5 has worked to keep the country safe over the past 115 years.”

The exhibition traces the technological evolution of espionage through artefacts such as MI5’s first camera, purchased from the Army and Navy store on Victoria Street by William Melville, considered the founding father of MI5 investigations. Also featured is a Robot Star 50 concealment camera used extensively during the Cold War, which was small enough to be hidden inside clothing with its smallest lens concealed behind a button.

Visitors can examine items from both ends of the political extremism spectrum that MI5 monitored, including a key to the Communist Party of Great Britain’s Westminster offices and a British Union of Fascists armband belonging to Mitzi Smythe, a German woman interned in 1940 alongside Oswald Mosley in Holloway Prison.

“From capturing the intrigue of counter-espionage and the daring double-agents during the world wars, to chilling Cold War confessions, and the counter-terrorism of recent times, these are the real stories that have helped inspire so many novels, TV dramas and big-screen spy thrillers we’ve come to love,” said Mark Dunton, curator of the exhibition.

The chronological display covers MI5’s formation before the First World War, its fight against fascism during the Second World War, the spies and scandals of the Cold War, and contemporary counter-terrorism operations.

Saul Nassé, Chief Executive at The National Archives, added: “We are thrilled to be working with MI5 on this exhibition, and the objects they have shared tell their story in a compelling way. Placing these artefacts alongside the files, papers, and photographs already in The National Archives’ collection allows us to provide new insights and perspectives into MI5’s activities during some of the key periods in modern British history.”

“MI5: Official Secrets” runs until 28 September 2025, with free admission.