Princess Diana and Prince Charles marriage breakdown has made headlines for decades, but a new book claims that the two were at odds long before they publicly announced their separation

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Princess Diana and Prince Charles‘ marriage breakdown has been making headlines for decades, but a new book claims that the two were at odds long before they publicly announced their separation — with Charles seeking help with their relationship as early as their honeymoon.

Royal writer Sally Bedell Smith claims in her new biography on the Prince of Wales, Prince Charles: The Passions and Paradoxes of an Improbable Life, that a mixture of both the couple’s gaping age difference and Diana’s emotional and mental state put a strain on their romance. She also writes that Diana’s reluctance to take prescribed medication and keep up with therapy — as well as Charles’ inexperience with dealing with someone with emotional issues — led to their breakup.

As previously reported, Bedell Smith claims that Charles felt pressured into marrying Diana after his father, Prince Philip, sent him a note about risking the young society girl’s reputation if he didn’t decide what to do. But Bedell Smith also writes that a few of Charles’ friends advised him against proposing to Diana.

According to Bedell Smith, Penny Romsey, the wife of Louis Mountbatten’s grandson Norton Knatchbull, cautioned the prince against marrying Diana due to their age difference and the fact they didn’t have a lot in common. (Diana was 12 years his junior.) Bedell Smith also writes that Romsey didn’t think Diana’s intentions were genuine and thought she appeared to be “auditioning for a central role in a costume drama.”

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Prince Charles and Princess Diana on their honeymoon in Balmoral in 1981
| Credit: Anwar Hussein/WireImage

Charles eventually went to marry Diana, even though, as Bedell Smith writes, he apparently privately told friends about his anxiety and uncertainty about the match. According to the author, Charles even cried the night before his wedding as he was still torn over his love for his ex-girlfriend Camilla Parker-Bowles.

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Princess Diana and Prince Charles in Canada
| Credit: Tim Graham/Getty

Charles’ godmother, Patricia Mountbatten, said that he had second thoughts about the wedding — something Diana admitted to as well later on — but he was afraid it would reflect badly on the future princess if he broke things off.

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Princess Diana and Prince Charles on their wedding day, 1981
| Credit: Anwar Hussein/WireImage

“He realized that if he called it off, it would ruin Diana’s future,” she said. “If Prince Charles didn’t want her, who would?”

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Bedell Smith also writes that Diana’s admitted personal issues also took a toll on the marriage. (Diana revealed in her infamous 1995 Panorama interview that she suffered from depression, bulimia and had engaged in self-mutilation.) She writes that during the couple’s honeymoon in Balmoral, the Princess of Wales would clash with her husband and cry for hours on end. According to Bedell Smith, Charles invited his “guru,” philosopher Laurens van der Post, to Balmoral to help Diana, ultimately leading the philosopher to advise that Diana needed psychiatric help from van der Post’s friend, Dr. Alan McGlashan.

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Princess Diana and Prince Charles in 1992
| Credit: Anwar Hussein/Getty

According to Bedell Smith, Diana initially sought treatment and was prescribed Valium (diazepam), a drug often used to treat anxiety and depression. However, the author writes that Diana refused to take the drug after she became convinced that the royal family was trying to sedate and control her. She also stopped attending therapy with Dr. McGlashan after eight visits.

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Prince Charles and Camilla Parker-Bowles
| Credit: Hulton-Deutsch Collection/CORBIS/Corbis via Getty

Unfortunately, according to Bedell Smith, Charles was unable to fully understand and deal with Diana’s personal issues — although she writes that he was sympathetic. Bedell Smith also writes that while Queen Elizabeth II and Philip noticed the couple’s strained relationship and Diana’s changing moods, they didn’t speak to their son about it and he kept it mostly hidden.

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The couple’s marriage famously fell apart and the two would get into frequent arguments. Bedell Smith writes that Charles’ cousin Pamela Hicks claimed that Diana would “hit him over the head and keep on with the row while he was praying.”

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Princess Diana (left) and Queen Elizabeth II in 1987
| Credit: Georges De Keerle/Getty

Eventually the couple would divorce in 1996 after years of separation, estrangement and embarrassing revelations about Charles’ continued relationship with Camilla. Despite the bitter split, Charles was distraught when he found out about Diana’s death in 1997, but was also keenly aware of the public’s affection for the princess — and how they sided with her throughout the divorce.

Shortly after her death, Bedell Smith writes that Charles asked his courtiers, “They’re all going to blame me, aren’t they?”

Prince Charles: The Passions and Paradoxes of an Improbable Life (Random House) will be released on April 4.