The most valuable precious stones from the Crown Jewels were hidden in a cookie tin and buried at Windsor Castle to keep them from being stolen by the Nazis during World War II, according to a new report.

According to the Times of London, King George VI, the father of Queen Elizabeth II, reportedly ordered that the drastic action be taken and the key gems were carefully removed from the Imperial State Crown and were put in a Bath Oliver cookie tin before being buried in a hole at the castle.

Previously, rumors swirled that the Crown Jewels were stashed a cave in Wales or a vault in Canada during WWII. But Alastair Bruce, an expert on the Crown Jewels, has solved the mystery after he discovered letters from the royal librarian Sir Owen Morshead to Queen Mary, George VI's mother, that show where the prized objects were stashed according to the Times.

According to the British newspaper, a deep cavern was dug beneath one of the secure entries to Windsor Castle and two chambers, complete with steep doors, were constructed. Access to the hole was created through a trapdoor that still exists today, Bruce told the paper.

The Black Prince's Ruby and St. Edward's Sapphire that were removed by Morshead and put in the cookie tin, according to the paper. This was to ensure they could be kept separately in the event of an emergency.

"He just gorged them out, recognizing there would be plenty of chances to put them back in again, wrapped them up and put them in the Bath Oliver tin so should anything happen – just as when Oliver Cromwell ordered the Crown Jewels to be smashed up – they could ferry these away and could rebuild it in due course," Bruce told The Times.

And the Queen – who would have been about 14 at the time — was told of the plan apparently for the first time in a groundbreaking documentary that airs on Smithsonian Channel on Sunday. In the documentary, the Queen opens up about her 1953 Coronation and wearing that famous crown.

"What was so lovely was that the Queen had no knowledge of it," Bruce told the Times of the cookie tin plan. "Telling her seemed strangely odd."

This Story Originally Appeared On People