Queen Elizabeth II reveals a secret of the crown in candid documentary

Queen Elizabeth II and Prince Philip, Duke of Edinburgh, on the balcony at Buckingham Palace, following her coronation at Westminster Abbey on June 2, 1953. (Leslie Priest / AP)

LONDON -- Queen Elizabeth II has revealed the secrets of giving a speech while wearing a weighty crown, in unusually candid comments in a new documentary on her 1953 coronation and the symbolism of the crown jewels.

Among the revelations of the BBC program airing Sunday is that the crown jewels were kept safe during World War II by being hidden in a biscuit tin buried at Windsor Castle. Although it was known the jewels had been taken to the castle 20 miles (32 kilometres) west of London for safekeeping, details had not been widely discussed.

The queen also discusses the challenges of being head of state. She jokes that she can't look down while wearing the Imperial State Crown -- which weighs 2 pounds 13oz (1.28 kilograms). The crown is worn by the monarch when delivering a speech for the State Opening of Parliament.

"You can't look down to read the speech, you have to take the speech up. Because if you did, your neck would break. It would fall off," the queen said in excerpts released ahead of the program. "So there are some disadvantages to crowns, but otherwise they're quite important things."

In the program, the queen notes that the crown has been reduced in height since being worn by her father, King George VI.

"Fortunately, my father and I have about the same sort of shaped head," the queen said. "But once you put it on, it stays. I mean, it just remains on."