Prince William and Prince Harry's late mother Princess Diana did not reportedly think her ex-husband Charles was "cut out to be king."
Diana, before her tragic death in 1997 car crash, had shared her thoughts about Charles' future role as monarch to Jennie Bond, a former royal correspondent for the BBC.
Princess Diana revealed that Queen Elizabeth II’s eldest son struggled with his role as heir, Bond recently told The Telegraph.
Christopher Andersen, author of "The King," told Fox News Digital Diana questioned whether "The Boy Wonder," as she referred to Charles, could step up to the role when the time came.
"Diana said on several occasions that she knew she never would be queen and that she was convinced that Charles would never be king," Andersen explained.
The author added: "She was a great believer in signs and omens and dreams, and they were all telling her that [Prince] William, not Charles, would succeed Elizabeth II. [But] she was wrong about that and a lot of other things."
Andersen noted that Diana would have likely been horrified by the thought of her former husband’s mistress being crowned beside him. She referred to the former Camilla Parker Bowles as "The Rotweiller," Andersen said.
"Diana would have been absolutely gobsmacked by the thought of Camilla marrying Charles, much less being crowned queen beside him," according to Andersen.
Diana, who was also known for giving nicknames, referred to Camilla as "The Rotweiller," while Charles was coined "The Boy Wonder," according to Andersen.
Diana told Bond from her Kensington Palace home she felt Charles was "never cut out to be king" and had "enough problems" as heir to the throne.
"The truth is that Charles would be much happier living in Tuscany, painting the landscape or studying architecture," she told Bond.
According to the same outlet, Bond also claimed Diana felt Charles needed to overhaul some of his patronages. The outlet noted that, at the time, he had already been working with several environmental charities and organizations for 30 years.
Diana's former butler Paul Burrell previously claimed that Charles could be too old to take over from the Queen.
Barbra Streisand's memoir reveals endearing friendship with King Charles III
Meghan Markle's mystery unveiled - Anticipation grows for her next career move
Meghan Markle orchestrated marriage for money, notoriety, and title, Carter suggests
Inside scoop on Prince Harry and Meghan Markle's royal experience
Meghan Markle's close to inking a highly lucrative contract
Meghan Markle's quick thinking saves the day in Royal script mix-up