Prince Harry will be "gathering anecdotes for his next assault on his family" when he returns to the UK for King Charles' Coronation, according to Paul Burrell.
The Duke of Sussex will attend the historic event without his wife Meghan Markle, who will remain in California with their children Prince Archie and Princess Lilibet.
Princess Diana's former butler Paul, 64, has said Harry will find it very difficult when he has to "kiss the hand of Queen Camilla" following the fallout from his tell-all memoir Spare.
In the book, Harry branded his stepmother a "villain" and warned she was "dangerous".
He also said he had "complex feelings about gaining a step-parent who I thought had recently sacrificed me on her personal PR altar".
"Harry is keeping the door open and preserving his unique selling point by being Royal. That's what the Americans love, the fact they're Royal.
"Harry will have to face his family, the ones he has criticised. He will even have to bow and kiss the hand of Queen Camilla, and that's going to be a very tough pill to swallow," Paul said in a new interview.
Speaking to GB News, he added: "He will also be gathering anecdotes for his next assault on his family."
King Charles' Coronation falls on the same day as Archie's birthday, with a close friend of Meghan suggesting this played a key part in her decision to stay away.
However, Paul thinks she would have decided not to attend the big event even if it wasn't her son's birthday.
"The decision is exactly what I thought would happen," he said. "I personally did not want to watch the Harry and Meghan show at the King's Coronation, I want to watch the King's Coronation.
"It's right that she’s not here because I think her security would be in danger. She would be at risk of being booed or even worse.
"This excuse of her not coming because it's Archie's birthday is pathetic because Lilibet spent her first birthday here at Frogmore Cottages, so why couldn't Archie?"
The couples announcement ends months of speculation about whether or not they would be at the Coronation.
The Palace said in a statement: "Buckingham Palace is pleased to confirm that the Duke of Sussex will attend the Coronation Service at Westminster Abbey on 6th May.
"The Duchess of Sussex will remain in California with Prince Archie and Princess Lilibet."
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