Royal Book Reveals What Pushed Kate Middleton to Her ‘Limits’ With Brother-in-Law Prince Harry (Exclusive)

Royal expert Christopher Andersen’s new book reveals the moment Princess Kate Middleton was pushed to her “limits” with brother-in-law Prince Harry.

“The damage was done: seeds of doubt concerning the King’s chances for a full recovery had been sown,” Andersen writes in Us Weekly’s exclusive excerpt from Kate! The Courage, Grace, and Power of the Woman Who Will Be Queen, set to be released on Tuesday, May 5.

Anderson is, of course, referring to Harry’s May 2025 interview in which he discussed his ongoing rift with the royal family.

“I don’t know how much longer my father has,” Harry said at the time, which made Kate “more disappointed than angry,” per the excerpt.

“But William, who had already slammed the door shut on his brother over what Harry wrote in Spare, was, in the words of a courtier, ‘apoplectic’ with rage,” Andersen writes. “Now it was time to nail the door shut once and for all, and for the first time Kate, who had worked harder than anyone to mend the rift between the brothers, willingly handed her husband a hammer.”

Kate “promised” William that she “was done” with Harry after his bombshell BBC interview.

“Princess Catherine is ‘the sweetest, most loving person you could ever know,’ said a Sandringham staffer, ‘but like everyone else, she has her limits,’” Andersen’s excerpt reads.

Andersen also spoke with Us exclusively about the moment in his book.

“I think Kate’s relationship with her father-in-law over their shared cancer battles really has made her much more sensitive to King Charles’s feelings,” he explained. “She knows better than anyone that having someone publicly imply you may be at death’s door is horribly demoralizing.”

Charles went public with his cancer diagnosis in February 2024 and Kate announced hers the following month. Kate has since announced that she is in remission.

“I’m sure Kate must have felt stung by that comment as well, since she is in a situation very similar to the king’s,” Andersen added, noting that Kate has always been the “level-headed one” in the family feud attempting to “bridge the widening gap between the brothers” — but this changed things.

Andersen speculated that he doesn’t see Harry and Kate “having any sort of relationship” going forward. “At least not for the foreseeable future,” he added.

Kate! The Courage, Grace, and Power of the Woman Who Will Be Queen hits shelves on Tuesday, May 5.

For more from the royal family, pick up this week’s issue of Us Weekly.