Princess Diana
Princess Diana's bodyguard reveals when she decided to quit royal life. Pictured: Princess Diana and Prince Charles at Westminster Abbey, London, for a centenary service for the Royal College Of Music on Feb. 28, 1982. Getty Images/Fox Photos

Princess Diana's bodyguard has shared what prompted the late Princess of Wales to quit the royal life.

In "Guarding Diana," which will be re-released in paperback later this month and was excerpted exclusively for Robert Jobson's "Royal Podcast," her former personal protection officer shared how Princess Diana vented her frustrations after finding out about Prince Charles' secret holiday with Camilla Parker-Bowles. "Diana knew perfectly well the reason for her husband's trip," Ken Wharfe wrote (via Evening Standard). "She knew that he would be meeting Camilla and that they would be enjoying private time together."

The writer added that Princess Diana's frustration came to a head when press photographers snapped her in a bathing suit during a private swim to relieve the stress of "delivering her husband into his lover's arms." According to Wharfe, Princess Diana was provoked by the photographers' presence. "I want out of this once and for all," the People's Princess told him.

The royal bodyguard knew that Princess Diana was referring to "being a member of the royal family and the circus that surrounded it." However, Princess Diana was reportedly already preparing for her divorce with Prince Charles at the time with her biography "Diana: Her True Story," which she worked on with Andrew Morton.

According to Lady Colin Campbell, Princess Diana asked her to write her official biography. She initially agreed, but decided to walk out when she realized that the princess wanted her to write lies.

"'Diana In Private' started out as the official biography. Diana and I agreed that I'd do an official biography of her — an anodyne biography. Then she saw it was what she called her 'get out of jail card," Lady Colin said. "And she decided to turn it from an official biography to an unofficial biography, detailing her dissatisfaction with her life as a member of the Royal Family."

According to Lady Colin, Princess Diana was advised to play victim by her friends. However, she didn't agree as she felt that it would not do good to Princess Diana, her children and the royal family.

"She wanted me to effectively tell lies like propaganda. I'm not criticising Andrew Morton — he wrote what she told him," Lady Colin claimed. "He chose to believe all that she said and accepted it undiluted, while I was not prepared to do so."