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.

Sir Anthony Blunt, the surveyor of the Queen's pictures and distinguished art historian, finally confessed he had been a Soviet agent since the 1930s.