The Royal Family would "crumble at the moment" if it weren't for the Duchess of Cambridge, a royal author has claimed.
Tina Brown, whose new explosive book The Palace Papers was released this week, claims it would spell disaster for the Firm if Kate decided she wanted to leave like Meghan Markle.
Kate officially became a royal almost exactly 11 years ago when she married Prince William in a lavish wedding at Westminster Abbey.
Her popularity has remained high and earlier this year, she celebrated her landmark 40th birthday.
And speaking to the New York Post, Brown said: "If for any reason, she thought like Meghan, ‘I’m out of here, I can do much better,’ it would be a disaster.
“It would, I think, crumble at the moment without her because she’s the only modern, beautiful woman who’s well-educated, substantial in herself, who’s actually wanting to commit herself to the rigours of this institution. Not many young women could do that.
Brown's comments come as another royal expert claims in their book that Kate and husband William have "blistering rows" and both "give as good as they get".
In William at 40: The Making of a Modern Monarch, which has been serialised in the Daily Mail ahead of its release next month, he shares details of the couple's relationship.
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He saws that William "is a bit of a shouter" while Kate is more of a calming influence.
Speaking to the author, an aide said: "He can be a bit of a shouter when he loses it. It’s fair to say the Duke and the Duchess give as good as they get if their disagreement results in raised voices.
"But they know each other so well, it usually blows over quickly – and she is, on the whole, a major calming influence on him."
He also details the positive influence Kate has had on William, largely down to her middle-class upbringing, which Robert claims has kept William grounded.
He said: "They’ve got a solid relationship and she gives him confidence. ‘There is no jealousy, no friction – they are happy for each other’s successes."
In the new book, Robert also looks ahead to William's role as King - but believes he'll be a very different Monarch to the Queen and Prince Charles.
He claims William has been "thinking deeply" about what he wants his time on the throne to look like and doesn't believe he'll be as passive as his grandmother.
Robert also believes William will be more private than his predecessors and will be "more robust" at challenging advice from those around him.
