Edward VIII reigned as king from January 1936 until December of the same year, when he abdicated to marry American divorcee Wallis Simpson amid accusations of being a Nazi sympathiser.

Speaking at the Oxford Literary Festival on Sunday, royal expert Alexander Larman spoke of his research in the Royal Family’s archives for a book about the family during the Second World War.

He claimed a Royal archivist told him: “We are not in the business of protecting the Duke of Windsor’s reputation”.

According to MailOnline, he told the crowd: “The Nazis knew what they were doing and that’s because they had inside information [from the duke].

“I don’t think he wanted to see him [his brother King George VI] dead but he was in a position where he knew exactly where everyone was in Buckingham Palace.”

During the war the Palace was a deliberate target for the Luftwaffe as their High Command felt that the destruction of such an iconic building would demoralise the nation, whereas it had the opposite effect.

The Queen was famously to utter "I'm glad we have been bombed. Now I can look the East End in the face."

Throughout Hitler’s bombing campaign the Palace suffered nine direct bomb hits and one death - PC Steve Robertson in 1941.

The revelation came after Edward was said to have taught the Nazi salute to his then six-year-old niece the Queen, which surfaced in a home video clip.

The Sun defended publishing the footage of the Queen, saying it was of great public importance and historical significance because of the involvement of Edward.

In an editorial column the newspaper said: “Here he is, in our pictures, apparently teaching his royal nieces the same Nazi greeting he would give Hitler personally at his mountain retreat four years later.”

It defended the Queen Mother and the Queen, highlighting their own patriotism and courage during the Second World War, adding: “These images have lain hidden for 82 years. We publish them today, knowing they do not reflect badly on our Queen, her late sister or mother in any way.

“They do, however, provide a fascinating insight in the warped prejudices of Edward VIII and his friends in that bleak, paranoid, tumultuous decade.”

Edward also visited Hitler in 1936 and is claimed to have said the dictator’s takeover of Germany was “the only thing to do”.

Meanwhile, Hitler reportedly believed that “permanent friendly relations could have been achieved” if Edward had remained on the throne, and in 1940 Churchill tried to suppress a Nazi plot to restore the monarch to his former position.