The Imperial State Crown is carried through the Norman Porch of the Palace of Westminster during the State Opening of Parliament on May 09, 2012 in London, England

The Imperial State Crown is carried through the Norman Porch of the Palace of Westminster during the State Opening of Parliament on May 09, 2012 in London, EnglandImage: Getty Images

New letters have revealed that in order to protect the royal jewels from the Nazis, they were hidden In a biscuit tin, 60 feet below Windsor Castle on the order of King George VI 

The new documentary The Coronation, which features an interview with Queen Elizabeth about her coronation, reveals that the jewels were removed from their setting by a librarian and hidden in a Bath Oliver biscuit tin, before being placed in a chamber dug beneath Windsor Castle. 

Read more: The man who tried to steal the Crown Jewels

The truth was uncovered by royal commentator Alastair Bruce through old letters written to Queen Mary by King George VI, which outlined plans for the secret chamber. Not many knew of the jewel's hiding place, and in fact nd, a trap door still exists near the site at Windsor Castle.

What jewels were hidden?

One of the most important is the Black Prince's Ruby, which has been mounted on the Imperial State Crown since the days of Queen Victoria's rule. Despite the crown being remade in 1937, the ruby remains in place. St Edward's Sapphire, which is older then the ruby, is set in the cross of the crown. 

The Cullinan Diamond, which is set in the Queen’s scepter is another important gem that's believed to have been hidden during the war. 

 Queen Elizabeth II, accompained by Prince Philip, the Duke of Edinburgh, prepares to deliver her speech in the House of Lords during the State Opening of Parliament on May 9, 2012 in London, England

Queen Elizabeth II, accompained by Prince Philip, the Duke of Edinburgh, prepares to deliver her speech in the House of Lords during the State Opening of Parliament on May 9, 2012 in London, England