For a decade, Queen Elizabeth II lived without knowing that her own art advisor, Anthony Blunt, a trusted man in charge of overseeing the invaluable Royal Collection, was living a double life as a Soviet agent.

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.

Queen Elizabeth II was not officially informed for almost a decade that one of her most senior courtiers had confessed to being a Soviet spy, according to newly released MI5 files.