Under the threat of German invasion during World War II, Britain's Crown Jewels were hidden in a most unassuming place: a biscuit tin, buried 60 feet below Windsor Castle.

The new documentary The Coronation, which features rare footage of the Queen speaking about the day she was crowned, reveals the secret plan to keep the priceless gems safe from the Nazis. In the film, royal commentator Alastair Bruce went to Windsor Castle with Royal Librarian Oliver Urquhart Irvine to see where the stones had been concealed during wartime.

"I was aghast because I had no idea that they had been there. I knew that the Crown Jewels had been taken away from London but I was aghast that they were put into a sort of tiny place," Bruce tells T&C.

In the film, you see him venture down the sally port, a passageway created in the middle ages, to see the two chambers where the Crown Jewels were kept. "They dug down from the surface, cutting out the chalk," Bruce explains. "And they had to put tarpaulins over it at night so that the whiteness of the chalk wasn’t seen by enemy aircraft flying over. They might have gotten an idea about what was going on."

But perhaps the most striking part of the story was that the royal librarian at the time removed the most precious stones from the crown and placed them in a biscuit tin, so that if their hiding place had been discovered, they could be easily moved and concealed yet again.

"What fascinated me is the idea of the royal librarian gauging out the Stewart Sapphire, the Black Prince's Ruby, the Edward-the-Confessor sapphire, just gauging them out with a pen almost, and a knife, and sticking them into this little circular tin, and getting them ready so that they could be rushed away to an even more secure place."

"It's so primitive, and there’s something slightly amateur about it, and yet if Britain had been conquered by the Germans, it was probably the last thing anyone would have thought of," said David Royle, executive vice president of programming and production for Smithsonian Channel.

Up until the filming of this production, even Queen Elizabeth herself was unaware of the Crown Jewels' location during WWII. "I think what’s so delightful is the queen had absolutely no idea this had happened," Bruce said.

"We were told nothing. We were only children then," the Queen says in the film. "One was never told anything. It was a secret I suppose.”

In the U.S., The Coronation will air on the Smithsonian Channel January 14 at 8 p.m. ET/PT. For more information, visit Smithsonianchannel.com.

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Caroline Hallemann
Digital Director

As the digital director for Town & Country, Caroline Hallemann covers culture, entertainment, and a range of other subjects