Prince Harry risks destroying his reputation both in the U.K. and the U.S.A. if he puts Camilla in a bad light in his memoir.

There are concerns that the Duke of Sussex will slate his stepmother in his upcoming book, which he had promised to contain a truthful account of his life. Prince Charles is said to be worried that it will be an "excoriating takedown" of his wife and that his son will publicly blame her for his childhood trauma.

However, royal expert Jonathan Sacerdoti advised the 37-year old against speaking ill of the Duchess of Cornwall in his memoir. He said it would only destroy his reputation if it backfires and the public could end up sympathising with his stepmother instead.

"It might dent her reputation, depending on what he says. If there are things in there that people don't like about how she's behaved or interacted with the family, I don't know if that's the case," he told The Express.

Sacerdoti thinks that it could "also have the opposite effect in that Harry and Meghan are increasingly unpopular in the UK because of their activities and statements." He thinks that Prince Harry "revealing negative thoughts and opinions about Camilla may well actually help the British public accept her and like her because their public approval is dropping as time goes on, and hers is increasing."

He added that if Prince Harry and Meghan Markle discredit Camilla in some way in his memoir, then it could have "a negative effect on their intentions." On the contrary, it could have a "positive effect" on the duchess among the British public.

Sacerdoti's warnings come after a royal source said that Prince Charles and Camilla are worried about the reputational damage the book could do. There are concerns about Prince Harry's recollections of his stepmother's entry into the Royal Family. The duke reportedly did not approve of the Duchess of Cornwall becoming his father's great love. The Prince of Wales is believed to be worried that his son will blame his wife for much of what he believes went wrong in his childhood.

Kate Middleton
Camilla, Kate and Prince Harry share a carriage ride. AFP / Getty Images