The Queen Mother and her aides had always advised against it, believing it inappropriate. Elizabeth was certain she wanted to do it. Photo / Getty Images
They were the photographs that aides feared would "bring the monarchy down".
The Queen, head of state, epitome of dignity and composure, posing for the camera like a professional model, hands on hips, off hips, in pockets, out of pockets.
One of those was Angela Kelly, the Queen's dressmaker and close confidante.
"I stood by in disbelief - the Queen was a natural," she recalls in her new book The Other Side of the Coin, the Queen, the Dresser and the Wardrobe.
It was Kelly in whom the monarch had confided the "secret wish" she had held since she was young.
After years of sitting bolt upright for official portraits, assuming a look of carefully considered gravity, she longed for the freedom to be photographed more informally.
The Queen Mother and her aides had always advised against it, believing it inappropriate.
But some time later, when the dressmaker was working on her first book, she remembered the conversation, plucking up the courage to ask Her Majesty if she would consider modelling with her hands in her pockets.
"The Queen looked at me in amazement as I asked whether she knew the potential implications of the photographs," she recalls. "She didn't take long to answer: yes, she would do it and, yes, she was sure."
On the day in question, photographer Barry Jeffery began to explain how the photoshoot would progress.
"Within moments, the Queen raised her hand respectfully and Barry immediately stopped talking," Kelly writes.
"No Barry, this is how we're going to do it," she said. "Just keep the camera rolling."
"And we were off. 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."
Kelly was working with the Royal Collection at the time, which was publishing her book, but the extraordinary images were not well received.
"Their opinion was that these more candid photographs would bring the monarchy down and therefore they were not suitable for the public eye," she revealed. "Why they thought that, I have no idea."
Kelly's second book, published on Tuesday, offers a unique insight into life behind palace walls. The two women, despite their wildly differing backgrounds - Kelly is a Liverpudlian docker's daughter - enjoy an incredible bond.
But Kelly admits that she was once so conscious of her accent that she plucked up the courage to ask if she knew anyone who might give her elocution lessons.
The look on her face was "a picture" she recalls. "She simply asked, 'Why?'"
But Kelly eventually hit on the idea of asking the Queen to provide the lessons herself.
Sensing she was not going to give up, the monarch instructed her to say one word: furious.
"'Fyer-ri-ous," Kelly responded.
"No fee-or-ree-ous," said Her Majesty. When Kelly eventually cracked it, the Queen exclaimed: "Yes!"
"Her finger went up in the air, followed shortly by: 'Not sick as a parrot.' And that was it - my one and only elocution lesson, and from the Queen herself."
Displays of sentimentality are quickly quashed by the monarch, Kelly notes, as she describes how emotional she feels when the Queen puts on the crown.
"The magnificence of the moment takes my breath away every time," she says.
"Normally the Queen rolls her eyes and playfully tuts at me when she sees my eyes fill up," she admits.
Elsewhere in the book, extracts of which are published in Hello! magazine, Kelly reveals that the 93-year-old monarch is fond of Singaporean silk.
But because there is never enough time to visit the markets on official tours, the local tradespeople set up their stalls in the airport, allowing her to browse.
The Queen "loves a bargain" and is a "very modest lady" occupying only a handful of private rooms at Buckingham Palace, a bedroom, sitting room, dressing room and bathroom.
Kelly takes aim at those former members of palace staff who have sought to capitalise on their connections by describing her private sanctum, revealing that members of the family are the only men she has ever known to have access.
"There will always be people who will say anything for attention," she comments.
Kelly, who got the job in 1994 after impressing the monarch with her discretion whilst working as a housekeeper for the British ambassador in Berlin, reveals the monarch gave the book her personal blessing.
"It was a joy to reminisce with the Queen over these stories," she says.
It became the subject of great public debate, deemed by many to be a tacit signal of support for Europe, a subtle personal statement about Brexit.
But as the Queen's blue hat adorned with yellow flowers became a national talking point, Her Majesty was highly amused.
It had not occurred to anyone at the Palace that the hat, worn by the monarch to the 2017 State Opening of Parliament, might resemble the EU flag, Angela Kelly reveals in her book.
"It was a coincidence but, boy, did it attract a lot of attention, and it certainly made us smile," she writes.
Kelly explains how the Queen opted to wear a day dress instead of the traditional robe and Imperial State Crown to the ceremony after it was rescheduled because of the General Election.
"I already had in stock some material suitable for Her Majesty's outfit, so after I'd checked the background against which The Queen would be sitting – to be sure that the colours wouldn't clash – I made the design and passed it, with my instructions, to the in-house dressmaker," she writes.
"Then the milliner, Stella (McLaren), and I sat down with a cup of tea to discuss the design of the hat.
"We chose a large square crown to balance the brim and five flowers, made from feathers with tiny seed pearls, painted yellow. It never occurred to Stella and me that people might think we were copying the European Union flag."
Guy Verhofstadt, the European Parliament's chief Brexit negotiator, posted a picture of the monarch on Twitter and joked: "Clearly the EU still inspires some in the UK."