Before Prince Charles married Princess Diana, he had feelings for Camilla Parker Bowles. Although Camilla was already married, and Diana was the girl that the royal family approved of, the Prince of Wales couldn’t turn off the love he had for Camilla.

Charles’ feelings for his former flame reportedly caused problems in his relationship with Diana long before their wedding. One royal biographer claimed that Prince Charles’ love for Camilla broke Diana’s heart.

In the book, “Charles: A biography,” Anthony Holden claimed that shortly after Charles and Diana announced their engagement in 1981, she became emotional after learning that Camilla was the woman he wanted.

The author revealed Princess Diana visited the palace to bid Prince Charles farewell before he embarked on a royal tour of Australia and New Zealand. However, the couple’s goodbye was interrupted when Charles received a phone call.

When Charles answered the phone, Diana realized it was Camilla and exited the room to avoid listening to their conversation. Almost 10 years later, Princess Diana told Holden the incident “just broke my heart.”

“She was weeping because her last minutes alone with the prince at the Palace had been interrupted by a phone call. It was Camilla, wanting her own fond farewell. So tender was the conversation that Diana had felt obliged to leave,” the author wrote.

“Left alone in the vast emptiness of Buckingham Palace, she went into a spiral of decline from which she was never really to recover throughout the fifteen years of marriage ahead.”

Although Princess Diana gave birth to two sons, Prince William and Prince Harry, she and Charles were unhappy in their marriage. The Prince of Wales began having an affair with Camilla and eventually separated from his wife.

Prince Charles and Princess Diana finalized their divorce in 1996. The Prince of Wales went on to marry Camilla in 2005.

Prince Charles and Princess Diana
Prince Charles and Princess Diana are pictured at an official event during their first royal Australian tour 1983 in Newcastle, Australia. Patrick Riviere/Getty Images