When Princess Diana’s marriage was deteriorating behind palace doors, the heartbroken royal turned to her mother-in-law, but her pleas went unanswered.

The claim was made by Ingrid Seward, editor-in-chief of Majesty magazine and author of "My Mother and I." The book explores King Charles’ relationship with his mother, Queen Elizabeth II. England’s longest-reigning monarch died in 2022 at age 96.

"Diana used to go to her private room in between appointments that the queen had, which were every 20 minutes, and burst into tears," Seward told Fox News Digital. "[She would[ say], ‘Everybody hates me mama, and I hate my husband. He’s a nightmare.’

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Queen Elizabeth, Princess Diana and Prince Charles standing next to each other and looking serious

Ingrid Seward claimed Princess Diana (center) attempted to reach out to her mother-in-law Queen Elizabeth II (left) as her marriage to the former Prince Charles (right) crumbled. (Tim Graham Photo Library/Getty Images)

"The queen would just stand there [horrified], and Diana would be getting more and more hysterical," Seward claimed. "[The queen] didn’t know how to handle it, but she thought Charles should know how to handle it. That was a very low point in the relationship."

Diana and Charles were first introduced in 1977 by her sister, Lady Sarah McCorquodale, who briefly dated the prince. The pair wouldn’t date until three years later, People magazine reported. After a whirlwind courtship, the couple married in 1981.

Despite what seend a fairy tale wedding, the union was plagued with problems. In 1986, Charles confirmed in an authorized biography that he began an affair with his longtime love, Camilla Parker Bowles, in 1986.

The book cover of Ingrid Sewards My Mother and I

Ingrid Seward has written a new book, "My Mother and I." (Simon & Schuster)

In 1992, Diana confirmed her marital woes in Andrew Morton’s book, "Diana Her True Story." In it, she detailed her mental health struggles while attempting to navigate royal life. Diana said she suffered from bulimia and suicide attempts.

Charles and Diana separated in 1992. The divorce was finalized in 1996. Diana died in 1997 from injuries she sustained in a car crash. The Princess of Wales was 36. Charles and Camilla married in 2005.

According to Seward, the queen wondered why her son, the heir to the throne, struggled to save the marriage.

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Princess Diana looking down at Queen Elizabeth and speaking to her

Ingrid Seward said Queen Elizabeth II (left) couldn't understand why her eldest son couldn't handle his marriage to Princess Diana (right). (Jayne Fincher/Princess Diana Archive/Getty Images)

"It had a huge impact," Seward explained. "The queen couldn’t understand how her son, who was in his early 30s, couldn’t handle a woman who was only in her early 20s. And she didn’t understand because she didn’t have the experience to understand something like that.

"Remember the cloistered world of the royal family, especially in those days," Seward continued. "They didn’t have to ever deal with moral conflict because there was always someone else to do it for them. If you didn’t want to talk to someone, the switchboard at Buckingham Palace would just not put them through. So, you never had to take on things. And the queen wasn’t used to doing this."

For the 25th anniversary edition of "Diana: Her True Story," Morton published a transcript of Diana’s interviews in which she described her cries for help.

Andrew Morton holding a copy of his book

Princess Diana rocked the monarchy when she leaked shocking details of palace life to author Andrew Morton. (Chris J. Ratcliffe/AFP/Getty Images)

"I threw myself down the stairs [at Sandringham]," said Diana, as quoted by Newsweek. "Charles said I was crying wolf, and I said I felt so desperate, and I was crying my eyes out, and he said, ‘I’m not going to listen. You’re always doing this to me. I’m going riding now.’"

The incident took place when Diana was pregnant with her firstborn, Prince William.

"So I threw myself down the stairs," said Diana, as quoted by the outlet. "The queen comes out, absolutely horrified, shaking – she was so frightened. I knew I wasn’t going to lose the baby; quite bruised around the stomach."

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Princess Diana and Queen Elizabeth standing opposite sides from each other looking away

Queen Elizabeth II and Princess Diana attend a polo match at Guards Polo Club May 30, 1982, in Windsor, United Kingdom. At the time, Diana was pregnant with Prince William. (Anwar Hussein/Getty Images)

"Charles went out riding and when he came back, you know, it was just dismissal, total dismissal," Diana shared. "He just carried on out the door."

Seward said that looking at the doomed marriage decades later, it’s easy to see why it failed.

"Charles wasn’t a very mature man," she said. "She was incredibly immature. They were completely unsuited. Diana said many, many, many years later to me, ‘If only we’d met at a different time in our lives.’ Diana was 19 when she met Charles, and she was a very naïve 19. She had a fixed idea in her mind of what she thought Charles was, and he wasn’t at all."

Prince Charles looking confused at Princess Diana as she has her back towards him

Ingrid Seward felt Prince Charles and Princess Diana were too immature for each other. (Tim Graham Photo Library/Getty Images)

Seward alleged in her book that the late queen thought Diana would have been better suited for her younger son, Prince Andrew, than her eldest. Charles and Diana had an age gap of 15 years between them.

"Andrew was certainly much more Diana’s age, and they’d known each other," said Seward. "Diana used to go to parties at … Sandringham. … Diana would go and have tea with the royal children who were much more her age, which would [have] been Prince Edward and Prince Andrew. 

"The queen … said, ‘Oh, I thought she would’ve been suitable for Andrew,’" Seward said. "She thought that Diana was perhaps a little more in love with the idea of marrying a prince than the actual idea of what the person was like."

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Princess Diana in a carriage looking at Prince Andrew

Lady Diana Spencer (1961-1997) and Prince Andrew in a carriage during the Trooping the Colour ceremony in London, circa 1981. (Keystone/Hulton Archive/Getty Images)

Seward said she never had the chance to ask Diana about her brother-in-law, coined the "Playboy Prince" and "Randy Andy" by the tabloids for his high-profile romances with models and socialites. Seward insisted they were always pals and nothing more.

"I think they always used to get on very well, and they laughed a lot together," said Seward. "I’m sure Andrew thought she was wonderful, but she probably wasn’t his type really. … He always liked quite sophisticated women, and I don’t think Diana would’ve put up with him. But I think they got along very well as friends."

Andrew married Diana’s friend, Sarah Ferguson, in 1986. The couple called it quits in 1996.

Princess Diana in a bright blue dress smiling next to Prince Edward in a suit and tie

Ingrid Seward doesn't believe Princess Diana and Prince Edward would have been an ideal royal match. (John Shelley Collection/Avalon/Getty Images)

When asked if anyone within the palace thought Diana would have been a better match for Edward, Seward quickly replied "No."

"I don’t think Diana and Edward were at all alike," she said. "I’m not sure that they really liked each other very much. Edward was very, very different from Diana. And no, they weren’t even particularly good friends. So that was never in the cards."

Edward has been married to Sophie, Countess of Wessex, since 1999.

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Prince Edward and Sophia standing together in front of a blossoming tree

Prince Edward married Sophie Rhys-Jones in 1999. (Ken Goff/Getty Images)

According to Seward’s book, Diana’s father, Earl Spencer, convinced his daughter that she shouldn’t call off her wedding to Charles.

It was at Andrew’s 21st birthday party at Windsor Castle that Diana was hoping to dance with her fiancé. Instead, the prince "spent the entire evening dutifully working the room and making sure he spoke to as many people as possible."

"Diana was in despair," Seward wrote. "Her fiancé had been away in America for most of the previous week, yet he clearly had no desire to dance with her. Feeling emotionally drained, she threw herself into dancing frantically with one man after another – and finally just dancing by herself."

A shy Lady Diana Spencer looking up.

Lady Diana Spencer (1961-1997), fiancée to the Prince of Wales, leaving her flat at Coleherne Court in Earls Court, London, circa 1980. (Central Press/Hulton Archive/Getty Images)

Seward claimed that footman Mark Simpson spotted Diana "looking exhausted and lost in her thoughts yet still moving in slow, rhythmic time to some tune in her head." Seward wrote that Diana later left the party "distraught, flustered, angry and had no intention of ever going back.

"But when she explained her decision to her father, Earl Spencer, he was appalled," Seward wrote. "After calming her down, he pointed out it would be an act of gross discourtesy to break off her engagement to the future king so close to the wedding.

"And, anyway, wasn't it what she'd always wanted?" she continued. "Didn't she remember him telling her that she should only marry a man she loved – and her firm reply: ‘That is what I am doing?’ Diana wasn't immediately convinced."

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Princess Diana in a bridal gown having her hand kissed by her groom Prince Charles

The Prince and Princess of Wales married on July 29, 1981. Diana wore a wedding dress by David and Elizabeth Emmanuel and the Spencer family tiara.  (Terry Fincer/Getty Images)

But eventually, after "gusts of tears and spells of indecision," Diana "allowed her father to talk her round."

"She couldn't deny that she still wanted to be the Princess of Wales," Seward wrote. "And, at 19, she was young enough still to believe in happy endings, despite what her instincts had told her on that terrible night."