It’s difficult to imagine coming back from this one.

It’s not a secret that Prince Charles and Princess Diana had, for the most part, a tumultuous marriage—but one comment the former Prince of Wales said to his wife during a heated argument crossed the line.

According to Diana’s former butler Paul Burrell, whose book The Royal Insider: The Queen, the King, and Princess Diana comes out next January, during one tense exchange Charles revealed he “never loved” her during “one of their epic arguments,” with Burrell adding that Charles said, “I only married you to have children.”

Princess Diana and Prince Charles on their July 29, 1981 wedding day.Getty

In an excerpt serialized by The Daily Mail, Burrell wrote, “I didn’t realize that I had entered a war zone when I left the Queen’s [Elizabeth] service in 1987 to work for Charles and Diana.” At that time, Charles and Diana, who married in 1981, were still five long years away from their 1992 separation and eventual 1996 divorce. Charles had taken up again with his mistress, Camilla Parker Bowles, and Burrell wrote that Diana “always loved Charles, but she despised Camilla Parker Bowles, the ‘other woman.’”

According to Burrell, Diana said of Charles that “He never wanted a lover. He wanted a mother.”

Prince Charles and Princess Diana on April 8, 1983.Getty

After Prince William’s birth in 1982, “It wasn’t until [Prince] Harry was born on September 15, 1984, just over two years later, that her fate was confirmed,” Burrell wrote. “Charles came into the hospital room, looked in the cot, and said, ‘Oh, red hair.’”

When Diana responded that red hair ran in the Spencer family—her birth family—Charles seemed unimpressed. “He said, ‘Well, at least I’ve got my heir and spare now and I can return to Camilla,’” Burrell wrote.

To this, Diana told her royal butler, “I cried myself to sleep that night knowing that my marriage was over.”

Prince Charles and Princess Diana.

Prince Charles and Princess Diana.Tim Graham

“‘I gave him four good years and he was gone,’” Diana allegedly told Burrell. “‘And for the rest of the time I had to pretend and put on a facade for the world.’”

Even through all of this, Diana was committed to her marriage, according to Burrell, and didn’t want it to end. “Diana never wanted a divorce,” Burrell explained. “Despite everything that happened, I have no doubt that Diana fell in love with Prince Charles. Unfortunately for Diana, the feeling was not mutual.”