The newly-declassified documents include details about some of the UK's most notorious spies.

The National Archives has released declassified MI5 files, including the confession of a civil servant who worked in the Cabinet Office, Treasury and Foreign Office in the 1930s, 1940s and 1950s – and spied for the Soviet Union at the same time.

Newly declassified British documents show that Queen Elizabeth II wasn’t told details of her long-time art adviser's double life as a Soviet spy because palace officials didn’t want to add to her worries.

Anthony Blunt, a royal art historial, confessed in 1964 to spying for the Soviets, but the late queen was not officially told about his past until 1973. View on euronews

Queen Elizabeth II was not told about her long-time art adviser's double life as a Soviet spy, newly declassified documents reveal.

Recently declassified MI5 files have shed light on one of the most infamous chapters in Cold War espionage, revealing previously hidden details about Soviet infiltration in Britain's intelligence establishment and the royal household.

Queen Elizabeth II wasn’t told details of her long-time art adviser's double life as a Soviet spy because palace officials didn’t want to add to her worries, newly declassified documents reveal.

Documents newly declassified by MI5, Britain's internal intelligence agency, show the late Queen Elizabeth II was not informed for almost 10 years that a member of her staff had spied for the then-Soviet Union.

Sir Anthony Blunt, the royal family's picture surveyor and renowned art historian, finally admitted that he had been a Soviet agent since the 1930s