Princess Diana was ready to put royal protocol to the test to prove she was a "free woman."

The late Princess of Wales is the subject of the upcoming "Princess Diana’s Style & A Royal Collection" auction, which takes place on June 26 in Los Angeles. It will feature some of fashion designer Jacques Azagury’s design illustrations for Diana, and fabric swatches from some of her famous dresses.

"It feels wonderful [to keep her memory alive]," Azagury, who helped Diana revamp her style during her final years, told Fox News Digital during a private preview at The Peninsula Residences London. "Anything that I can do that’s going to carry on the legacy of the princess, I will always do it… It’s a way of keeping her alive really."

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Azagury said he met Diana in 1985 when he was showing his new collection in London. They were introduced by Anna Harvey, deputy editor of British Vogue.

"She immediately put me at ease," he described. "She had this amazing ability to make you feel completely at ease in no time."

In return, Azagury would help Diana step out of her shell.

"In her later years, Diana embraced this sexier, sleeker look, which was my aim," he explained.

"My aim was really to just get her out of all these frills and… frumpy skirts that she was wearing at the beginning. As her life was developing, she had to be on the international stage, and it was my job to make her fit there. Gradually, I simplified and simplified her right to the end until there wasn’t really that much dress. It was more about the princess and the fit of the dress."

According to reports, British royals are subject to strict fashion rules. And as the wife of the future king, Diana was expected to follow them. But as her marriage publicly crumbled, Diana was ready to send a new message using her style.

WATCH: PRINCESS DIANA'S DESIGNER EXPLAINS WHY HE DENIED HER BOLD FASHION REQUEST

One of the most iconic looks was "The Revenge Dress," a slinky little black dress that she wore in 1994, on the same night that her ex-husband, the former Prince Charles, confessed his infidelity on national television. Reports claimed that Diana owned the Christina Stambolian design for three years, but never wore it until then because it was too daring.

Charles and Diana separated in 1992. Their divorce was finalized in 1996. And it was during the ‘90s that Azagury created "The Famous Five," a collection of dresses that showed Diana in a new light.

"This is a period when you see the Diana that we all loved, where she was feeling free from her marriage," said Azagury. 

"It was her new life starting. She was fit, she was training. She looked phenomenal, and these dresses were saying exactly what she wanted to say, that she was a free woman. She could wear what she wanted to wear. She moved away from royal protocol with the length of the dresses. It was kind of a rebellion, but not a rebellion. But it was her way of telling people that she’s her own woman."

But Azagury admitted he wasn’t prepared for Diana’s bold fashion request.

"[She surprised me] only once," he said.  "She wanted to go super short on the dresses, and we wouldn’t allow it, particularly on that blue [‘Swan Lake’ dress from June 1997]. It was quite a low décolletage and quite short anyway, and she wanted to go even shorter. We just said, ‘Look, you’re not going to have a dress left and you are a princess. We’ve got to remember you’re a princess.’ So it was way short anyway, so that’s really the only request we would not abide by."

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Azagury said that one of Diana’s favorite colors to wear was black, which, for the royals, is typically reserved for mourning. But the princess, who was thriving during the era of supermodels, wore several pieces by Azagury that were low-cut, figure-hugging, and showcased her bare, lean arms. Her "Venice" dress from 1995 was a bright red silk two-piece featuring a short skirt. The 1997 "Washington" dress featured a deep V cut in the back.

"After Diana’s marriage, she portrayed herself in a slightly different manner," Azagury explained. "She had total freedom… She could wear what she wanted to wear. She was able to wear black, which she's usually not allowed to wear because royals only wear black for funerals."

"So the minute she was away from that, the first dress we made for her… was a black dress we made for her after the Martin Bashir interview… a black sexy dress," he shared. "That was her way of saying, ‘This is me, this is the new me. I’m confident.' And it had all of those things in that one dress. She treated the dresses like that all the way through."

And as one of the most photographed women in the world, there was no room for error, Azagury stressed.

"As a designer, my main thing was to make sure that every single little thing on the dress was perfect," he said. "She was stepping out of her shell, and she would have 500 photographers surrounding her, so everything had to be perfect, even though the dresses were very, very simple."

"It took a lot of work to get everything immaculate, and that was my job," he said. "We never had any mishaps at all. We just didn’t want to end up in a circle of shame with a bit of something sticking out. So really, it was my job to make sure that everything was perfect for her."

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Azagury created what royal watchers have coined the "Final Goodbye" dress. It was a full-length black dress highlighting a plunging neckline, thin straps and a high front slit. Diana was fitted for it in London just before she flew to Paris.

"I think it might’ve been for a Disney premiere, so we wanted to make it more wow than the other dresses and make it really Hollywood red carpet," said Azagury. "All that had to be done was to [adjust] the straps. Sadly, she never got back to wear it."

But her legacy lives on, he said.

"The princess is still indirectly affecting fashion, affecting the other royals," said Azagury. "Of course, anytime that Kate wears something that possibly remotely looks like something Diana wore… it always gets compared in the newspapers. So, she’s still there."

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"In a way, the dresses that she wore at the time, yes, they were fashions of the time, but they were timeless pieces," he reflected. "Any of the dresses that I made, for instance, could be worn today, and they wouldn’t look out of place. There’s something to say about her dress sense… it went quite deep."

The auction "Princess Diana's Style & A Royal Collection" by Julien's Auctions kicks off June 26 at The Peninsula Beverly Hills.