Late queen was not officially told Anthony Blunt was Soviet spy for years

The decision to formally inform the queen came amid growing concerns in Whitehall that the truth would inevitably come out after Blunt, who had been seriously ill with cancer, died. Journalists were already investigating the story and they were no longer constrained by concerns of libel.

Suspicion first fell on Blunt in 1951, after when his fellow spies Guy Burgess and Donald Maclean fled to the Soviet Union.

He had been a close friend of Burgess since their time at Cambridge together in the 1930s – part of the so-called Cambridge Five group of spies.

During World War Two Blunt had worked for MI5, after 1951 he was interviewed 11 times by the Security Service, but always denied espionage.

Then the American Michael Straight told the FBI he’d been recruited by Blunt himself as a Russian agent.