Queen Elizabeth says her neck would "break" if she looked down while wearing the Imperial State Crown.
The 91-year-old monarch has to place her speeches at eye-level when she is wearing the 2.2lbs headdress to ensure she doesn't do herself a serious injury, or drop the heavy item from the top of her head.
She said: "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 [the crown] would fall off.
"So there are some disadvantages to crowns, but otherwise they're quite important things."
The queen admitted the crown was "unwieldy" when her father George VI was coronated but it was remodelled afterwards and made "much smaller".
Describing her dad's crown, she said: "Very unwieldy. Fortunately, my father and I have about the same sort of shaped head. But once you put it on it stays. I mean it just remains on."
Elizabeth has also revealed her dress became stuck during her Coronation - which took place in June 1953 at Westminster Abbey - and she "couldn't move at all".
She recalled: "Well I remember one moment when I was going against the pile of the carpet and I couldn't move at all. Yes, they hadn't thought of that."
On the way back from her Coronation, Elizabeth was transported in the iconic Gold State Coach, which weighs nearly four tons, and the royal has admitted it is "horrible" to sit in for long periods.
Speaking in an upcoming documentary to mark the 65th anniversary of her Coronation, she added: "It's not meant for travelling in at all. I mean, it's only sprung on leather. Not very comfortable.
"Halfway around London. It can only go at a walking pace. The horses couldn't possibly go any faster. It's so heavy."
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