The rift between Prince William and Prince Harry was the result of an angry phone call when William confronted Harry about reports that Meghan Markle had been bullying royal staff.

That’s the bombshell claim in Battle of Brothers: William, Harry and the Inside Story of a Family in Tumult, a new book by British historian Robert Lacey, historical adviser to “The Crown”.

According to an excerpt published in The Times, the royal rupture in the brothers’ relationship can be traced to a “furious” conversation between the brothers after William became aware of a memo from Kensington Palace communications secretary Jason Knauf detailing numerous complaints from staffers about the way they were being treated by the Duchess of Sussex.

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“I’m very concerned that the duchess was able to bully two PAs out of the household in the past year,” Knauf emailed William’s private secretary Simon Case in October 2018.

Knauf described Meghan’s behaviour toward one aid as “totally unacceptable,” writing that “the duchess seems intent on always having someone in her sights.”

Knauf also alleged that Meghan had bullied another member of the staff by “seeking to undermine her confidence.” In fact, he complained, his office had received “report after report” detailing “unacceptable behaviour” by the former “Suits” star toward Kensington Palace staff.

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“Meghan governed by fear,” one courtier alleged. “So many people said it. Nothing was ever good enough for her. [She] humiliated staff in meetings, [would] shout at them, [would] cut them off email chains — and then demand to know why they hadn’t done anything.”

According to the book, one aide told a colleague that “I can’t stop shaking” in advance of an encounter with Meghan, while another reported that her interaction with Meghan made her “feel sick.” In addition, another staffer accused Meghan of “emotional cruelty and manipulation, which I guess could also be called bullying.”

Some staffers claimed they were suffering from PTSD due to Meghan’s treatment, while “several” claim to have been “humiliated” by her.

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In addition, there were also allegations that Harry behaved similarly.

“I overheard a conversation between Harry and one of his top aides,” recalled a Kensington Palace courtier. “Harry was screaming and screaming down the phone. Team Sussex was a really toxic environment. People shouting and screaming in each other’s faces.”

According to the excerpt, William “personally knew and liked all the individuals whom Knauf had named in his dossier,” and was “horrified” by the allegations. He immediately called Harry.

However, “when Harry flared up in furious defence of his wife, the elder brother persisted. Harry shut off his phone angrily, so William went to speak to him personally. The prince was horrified by what he had just been told about Meghan’s alleged behaviour, and he wanted to hear what Harry had to say.” That face-to-face “showdown” was reportedly “fierce and bitter.”

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“Meghan portrayed herself as the victim,” one Kensington Palace staffer claimed, “but she was the bully. People felt run over by her. They didn’t know how to handle this woman. They thought she was a complete narcissist and sociopath — basically unhinged. Which was why the pair of them were drawn to each other in the first place — both damaged goods.”

Meanwhile, William felt “deeply wounded” by the experience, and came to the conclusion to split up the royal household at Kensington Palace, instructing Simon Case to immediately divide the two households.

“William wished to be separated from Meghan on a day-to-day basis — and that meant being separated from his brother as well,” noted the excerpt, which was when Harry and Meghan moved to new digs at Windsor

“William,” said a friend, “threw Harry out.”

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ET Canada has reached out for to the Sussexes’ representatives for comment.

Battle of Brothers: William, Harry and the Inside Story of a Family in Tumult will be published on June 24 .