Meghan Markle possessed a “dangerous level of self-belief” that the palace “didn’t know what to do with,” author Robert Lacey claimed in his upcoming book, Battle of Brothers.

According to the historian, there was a noticeable change in the dynamic between Prince Harry and his relatives when Meghan was introduced to the Royal Family — and it wasn’t long before she was deemed “difficult” for trying to upend the monarchy’s policy of “sticking together.”

The former Suits actress, who ditched her Hollywood career in the wake of forming a relationship with the Duke of Sussex in 2016, tried so hard to shake things up at the palace that the royals (including Queen Elizabeth II) pondered how to handle “the spare’s wife,” said Lacey.

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“What you’ve got to realize is that the whole strategy of the monarchy was based on them sticking together. Meghan changed all that,” Lacey explained. “She has an incredible and dangerous level of self-belief.”

Lacey, who is also credited as one of the consultants on the wildly popular Netflix series The Crown, uncovered that Harry’s conduct changed after meeting Meghan. According to the royal expert, Harry realized “there was something rotten at the heart of royelness that is not for him.”

In September, the Duke, 36, and Duchess, 39, of Sussex took part in a handful of interviews from their $14.7 million home in Montecito, Calif., to examine issues concerning diversity and race in the U.K. before urging voters in the U.S. to “reject hate speech, misinformation, and online negativity.”

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Last month, a spokesman for Buckingham Palace refused to comment on Harry, seeing as how he’s no longer “a working member of the Royal Family,” after sources asserted that the prince had violated his agreement with the Queen by involving himself in matters concerning U.S. politics.

It’s believed that his candid views on President Donald Trump have strongly implied that Harry plans on making the U.S. his permanent base, with no plans to return to the U.K. in the foreseeable future. As OK! previously reported, “Harry hasn’t made an application for dual citizenship or a green card yet, but he has met with immigration lawyers and is ready to begin the long process,” according to our source. “He is excited about his future and becoming an American.”

Meanwhile, Lacey believes that the Royal Family didn’t handle Meghan’s introduction into the palace the correct way, insisting that there was little to no opportunity for the former actress to conform to her new life.

“There is only one self-made millionaire in the Royal Family and that is Meghan Markle. If they had sat down with her at the start and said, ‘Let’s talk about the things you are interested in,’ things might have been different,” he claimed.

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“They made the mistake of dealing with the spare’s wife thinking she was just a routine royal. She was never going to be a routine royal.”

Battle of Brothers will be published on October 15, only weeks after the couple reportedly inked a lucrative deal with Netflix — and are already looking for more work. A source previously told OK!, “Meghan and Harry are hugely ambitious — and they’re not leaving anything to chance.”

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