The world of spies is murky. It is hard to know anything for certain, and people build careers on their ability to exploit that uncertainty. So it is fitting, amid the revelations about traitors Kim Philby and Anthony Blunt, that we should find the most sphinx-like figure of all, the late Queen herself.

The National Archives in Kew have released papers which purportedly spill the beans on one of the big unknowns of British public life from the Cold War era: when did Queen Elizabeth II learn that the ultra-respectable Keeper of the Queen’s Pictures, and one of the country’s most distinguished art historians, Sir Anthony Blunt, was a spy for the Soviet Union, having signed up with Moscow in the 1930s? Suspicion mounted around Blunt during the 1950s, and in 1964, after undeniable evidence emerged, he confessed in exchange for immunity from prosecution.

The Telegraph London