The Queen has posed for thousands of pictures since she took the throne in 1952.
But according to her royal dresser, Angela Kelly, there was one pose she'd always longed to have a portrait taken in, but was never allowed.
Angela revealed that she wanted a picture taken in a more informal pose, like with her hands in her pockets, but the Queen Mother and Queen Counselors had always asked her not to do as they were "not suitable for the public eye."
But Angela, who had known about the Queen's "secret wish" for several years, had a clever idea that would make it come true.
Writing in her new book The Other Side of the Coin, Angela revealed all.
She says: "I wondered if I might have a wonderful opportunity to make the Queen's wish come true."
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She nervously asked the Queen if she would "do her a favour" and pose with her hands in her pockets for an image in the book, reports Hello!.
She said: "The Queen looked at me in amazement as I asked whether she knew the implications of the photographs.
"She didn't take long to answer: yes, she would do it and, yes, she was sure."
On the day, Her Majesty was more than up for the challenge.
When photographer Barry Jeffery started speaking to the Queen about his plans for the shoot, Angela says the Queen raised her hand "respectfully" to tell him she knew exactly how she was doing it.
Angela writes: "Her Majesty took her position in front of the lens and started striking a series of poses, slipping her hands in and out of her pockets and placing them onto her hips, mimicking the stances of a professional model.
"I stood by in disbelief - The Queen was a natural Barry and I felt we were experiencing something really special: a moment never to be repeated."
When it came to choosing which pictures to feature in the book, Angela said that the Royal Collection wouldn't allow some of the more candid shots to be used as it would "bring the Monarchy down."
Angela also shared a number of other secrets in her book, like the bizarre backstory about the christening dress.
The gown is an exact replica of the intricate lace and satin piece which has been worn by all the royal babies in the family since 1841.
In 2004, the Queen asked Angela to make a new one as the original had become too fragile.
But to make sure the lace looked authentic she revealed that she dyed it with Yorkshire tea.
"We placed each piece of lace in a small bowl, from the Dressers' kitchen, filled with cool water and a teabag, and left it for about five minutes, checking regularly until the colour was perfect," she said.
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