Prince William was "smart" for waiting 10 years before proposing to Kate Middleton.

The claim was made by former Vanity Fair editor Tina Brown, who has written a new book about the British royal family titled "The Palace Papers: Inside the House of Windsor – the Truth and the Turmoil."

The bombshell book explores "the scandals, love affairs, power plays and betrayals" that have rocked the royals during the last 20 years. It promises to feature new revelations based on Brown’s access to palace insiders.

The bestselling author previously wrote a biography on the Princess of Wales titled "The Diana Chronicles," which was published in 2007.

PRINCE WILLIAM WAS ‘APPALLED’ BY QUEEN ELIZABETH'S CHRISTMAS PHOTO SNUB OF PRINCE HARRY, MEGHAN MARKLE: BOOK

Prince William Kate Middleton

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge, share three children. (Roland Hoskins - WPA Pool/Getty Images)

"He was absolutely sure she could handle [royal life] before they married," Brown told Page Six on Tuesday. "Nobody was deluded like Meghan [Markle] was, it seems."

The Duke and Duchess of Cambridge met in 2001 as students at the University of St Andrews in Scotland. William told The Telegraph they were friends for over a year before a relationship blossomed.

While the tabloids reported that the couple called it quits in 2007, they had reportedly gotten back together later that year. William proposed to Middleton in 2010 during a vacation in Kenya. The couple tied the knot in 2011.

William’s younger brother, Prince Harry, had a whirlwind romance with Markle, a former American actress. They met in 2016 on a blind date and the relationship was said to have gone from "0 to 60." In 2017, the Duke of Sussex proposed, and the couple said "I do" in 2018.

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Kate Middleton

Kate Middleton at graduation ceremony at St Andrews on June 23, 2005. (Anwar Hussein Collection/ROTA/WireImage)

Brown told the outlet that, unlike Markle, Middleton, 40, was better prepared to handle the pressures of royal life.

"If for any reason, she thought like Meghan, ‘I’m out of here, I can do much better,’ it would be a disaster," Brown explained. "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 rigors of this institution. Not many young women could do that."

Brown clarified that the term "Megxit," which was created by the press to describe the Duke and Duchess of Sussex’s departure from royal life, is incorrect. She argued that it was Harry, 37, not the former "Suits" star, 40, who suggested they should make their exit.

"I do think it’s wrongly called Megxit," said Brown. "He wanted out and she enabled him to do what he wanted. She was strong enough to say, ‘You know what? You want out. I can make it happen.' He’s shown ever since that he absolutely hates that whole life, doesn’t like it."

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Meghan Markle

Meghan Markle starred as Rachel Zane in "Suits." (Robert Ascroft/USA Network/NBCU Photo Bank/NBCUniversal via Getty Images)

"If not but for Meghan, he wouldn’t have found a way out because he basically was a man who had everything done for him all of his life," Brown continued. "He had never carved a life for himself. Meghan was very much a self-starter, a self-made successful woman. She knew who to call at Netflix. He wasn’t worldly like Meghan was worldly. They wanted to be global. If you want to be a global humanitarian superstar it’s going to take cash and that’s not going to be the same kind of money where you can live comfortably in Norfolk."

Brown also noted that Harry's father, Prince Charles, was hurt by his son's decision to step back, noting they had a close relationship at one point.

"They had a very warm relationship," she said. "It’s very upsetting to Charles apparently. He’s been distraught about the fraying of the relationship. He’s been very, very sad. He’s been very hurt by Harry."

A palace spokesperson didn’t immediately respond to Fox News Digital’s request for comment concerning Brown’s book. However, a spokesperson previously told Fox News Digital that the palace doesn’t generally comment "on such books." A spokesperson for the Duke and Duchess of Sussex also didn’t immediately reply to Fox News Digital’s request for comment.

PRINCE HARRY, MEGHAN MARKLE 'STUNNED' AFTER ROYALS 'SHUT THE DOOR,' BOOK CLAIMS: 'MUTAL ADDICTION TO DRAMA'

Meghan Markle Prince Harry

The Duke and Duchess of Sussex reside in California with their two children. (Patrick van Katwijk/Getty Images)

The Duke and Duchess of Sussex’s departures from royal duties began in 2020 over what they described as the British media’s intrusions and racist attitudes toward Markle. The family now resides in the coastal city of Montecito, California, with their two children.

In the wake of quitting royal duties, they gave an explosive TV interview to Oprah Winfrey in which the couple described painful comments about how dark Archie’s skin might be before his birth. The duchess talked about the intense isolation she felt inside the royal family that led her to contemplate suicide.

Buckingham Palace said the allegations of racism made by the couple were "concerning" and would be addressed privately.

The Associated Press contributed to this report.