When Princess Diana learned about Prince Charles’ affair with Camilla Parker Bowles she was furious. Before the couple announced their separation, she released a scandalous book that “utterly humiliated” her husband.

Although Charles married Diana in 1981, she suspected her husband was cheating on her with Camilla. Despite spending years in an unhappy marriage, she was heartbroken when she found proof of the affair.

Before the two publicly announced their split in 1992, Andrew Morton’s book, “Diana: Her True Story” was released. In 2005, Penny Junor published “The Firm,” which claimed Morton’s work embarrassed Prince Charles and the royal family.

“It painted the blackest portrait; not only called him a cold and faithless husband and a bad father, but it also questioned his fitness to be king. So much of it was demonstrably untrue, and so many stories were a distortion of the truth,” she wrote.

“People, who were witnesses to the events, remembered them in essence, but they had a twist to them, which always put the prince in a bad light. He was adamant, nevertheless, that there should be no retaliation and instructed his friends to say nothing.”

Although Princess Diana’s description of Charles hurt his image, Junor insisted the Prince of Wales never retaliated. “Charles has never publicly criticized Diana,” she stated.

However, he did release an authorized biography in 1994, in which he confirmed his affair with Camilla. Charles attempted to salvage his reputation by telling his side of the story, but his plan backfired.

After years of hashing out their split in the public eye, Prince Charles and Princess Diana finalized their divorce in 1996. Almost 10 years later, Charles married Camilla, who took on the Duchess of Cornwall title.

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