King Charles considered Queen Camilla 'non-negotiable' after Princess Diana, author claims

For King Charles, Queen Camilla was never up for debate — she was "non-negotiable."

The claim comes from British author Catherine Mayer's new book, "Divide & Rule," which explores history's most misunderstood royal wives ahead of Queen Camilla's July 17 birthday.

A spokesperson for Buckingham Palace told Fox News Digital they don’t comment on books.

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According to Mayer, multiple anonymous friends of the monarch said Charles "deemed Camilla's role in his life a 'non-negotiable,'" resulting in "painstaking" efforts to rehabilitate her public image.

"I think the non-negotiability was the point after the divorce and, of course, after Diana's death," Mayer told Fox News Digital. "He understood that this was the one woman who could really sustain him. And I think he felt the need for that kind of support, and Camilla has clearly always been prepared to do that."

"This is, in many ways, one of the most unlikely love stories you can imagine," said Mayer. "There were a lot of people who bought into the idea of the fairy-tale marriage between Diana and Charles. It was only when it imploded so spectacularly that they were forced to recognize that wasn't the truth of what had happened. And Camilla, at that stage, was seen as the other woman who had destroyed that relationship."

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"I personally don't think the relationship between Diana and Charles could ever have worked," Mayer continued. "But that doesn't mean I don't think Diana was very badly treated. ... [It's] terrible what happened to her. But with Camilla, you only need to see her and Charles together to understand that she has this ... magical effect on him. It's transformative."

Mayer, who previously wrote a biography of Charles, described "doggedly following him around" during her research. It was then that she saw Camilla’s undeniable hold over him.

"You would see him tired, very obviously out of sorts," she said. "And then she would come into a room, and he would light up. She just lifts him."

It was love at first sight for Charles when he met Camilla through mutual friend Lucia Santa Cruz in 1970. But according to People magazine, palace expectations got in the way. Camilla wasn't considered a suitable future queen because she wasn't a virgin and lacked the aristocratic pedigree many believed was expected of a future queen.

"She had something of a past," said Mayer. "Charles was looking for a virginal bride. Camilla was not somebody who was — I'm not trying to say she was a Mata Hari or a major league seductress. But she was somebody who enjoyed life. That's why he responds to her so much."

"At some point, she went off on a holiday in America, and she zoomed around on a motorbike in leathers," said Mayer. "She chain-smoked and was the life and soul of social occasions. And she had boyfriends, including the man she later married, Andrew Parker Bowles, who himself had a reputation for having a string of girlfriends."

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"This dusty, old-fashioned institution, they're telling the heir to the throne, 'This is the kind of woman you go off and have fun with, but not the kind you marry.' And if they'd been allowed to marry, history would be very different."

Royal broadcaster Ian Pelham Turner agreed.

"Camilla gave Charles, from the early days, a feeling of masculinity, making him feel sexual desire," he told Fox News Digital. "She treated him like a man rather than a royal."

Believing they didn't have a feasible future together, Charles and Camilla split. In 1971, Charles joined the Royal Navy, which kept him away from Camilla. In 1973, she married Andrew Parker Bowles, who previously dated Charles' sister, Princess Anne. Charles was said to be devastated, but the pair remained friends.

"The monarchy is really terrible at understanding what kinds of women should marry into it and how best to support them," said Mayer. "When Camilla came on the scene, she was seen as absolutely the wrong type of woman for Charles to marry."

Royal author Penny Junor previously claimed that Charles and Camilla reignited their physical relationship around 1978 or 1979, People reported. Parker Bowles reportedly was aware of the affair and "quite enjoyed the fact that his wife was sleeping with the future king," Junor wrote.

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Despite his relationship with Camilla, Charles began courting Lady Diana Spencer in 1980. Diana, a virgin born into an aristocratic family, was seen as an ideal match for the future king. They married in 1981 in what was described as "the wedding of the century."

Still, that didn't stop Charles and Camilla. People magazine reported they began seeing each other again in 1986, despite both being married with children.

"I think they did intend to break things off in terms of any kind of physical relationship, and they did," said Mayer. "But exactly when they rekindled it is another matter entirely because what they've said and what the evidence suggests don't always exactly match."

Turner told Fox News Digital Diana suspected early on that Camilla would never leave the picture.

"Camilla, without doubt, has been the love of Charles' life," he said. "He never stopped wanting to be with her, even when he married Diana. It has long been rumored that Diana recognized this before marrying Charles and tried to stop the wedding, but her father told her it was too late to back out."

During her marriage to Charles, Diana noticed he wore a pair of gold cuff links engraved with interwoven Cs, representing his devotion to Camilla.

"There was a famous incident described in Jonathan Dimbleby's authorized biography of Charles in which Diana found cuff links she realized were a gift from Camilla to Charles ahead of the wedding," said Mayer.

"The person I spoke to said there was a separate incident in which he lost one of the cuff links and became very upset about it. The suggestion is that these things had great meaning for him and that the friendship had great meaning for him."

In recordings made for Andrew Morton's book "Diana: Her True Story," the princess recalled confronting Camilla about the affair.

"I was terrified of her," Diana said, as quoted by People. "I said, 'I know what's going on between you and Charles, and I just want you to know that,'" she recalled.

"She said to me, 'You've got everything you ever wanted. All the men in the world fall in love with you, and you've got two beautiful children. What more would you want?' ... So I said, 'I want my husband. ... I'm sorry I'm in the way ... and it must be hell for both of you. But I do know what's going on. Don't treat me like an idiot.'"

She would later famously tell "Panorama," "There were three of us in this marriage, so it was a bit crowded."

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Charles and Diana separated in 1992. Their divorce was finalized in 1996. A year later, Diana died from injuries she sustained in a Paris car crash. She was 36. In 2005, Charles married Camilla. She was crowned Queen Camilla in 2023.

"In a lot of ways, Camilla has been very good for Charles," said Turner. "She's supported him in his efforts to become a great king. She has been his confidante, mentor and companion."

British broadcaster and photographer Helena Chard told Fox News Digital she agreed with Mayer's statement: When it came to Camilla, she was always "non-negotiable" for Charles.

"For years, the palace kept Charles and Camilla in separate boxes," said Chard. "Eventually, he chose love over protocol. Time did the rest. Camilla stayed steady, avoided the spotlight and carried out her royal duties. She became an asset, not a liability. By the time Charles took the throne, it was a no-brainer. You get the king, you get the queen. There was no plan B."