Prince William and Kate Middleton realized they needed to 'up their game' after Meghan Markle's first royal engagement, according to a new book

• A new book says the Fab Four's relationship changed after Meghan Markle's first royal engagement.
• Meghan exuded confidence, wit, and intelligence during a 2018 appearance, according to the book.

Prince William and Kate Middleton realized they needed to "up their game" after Meghan Markle's first royal engagement, according to "The New Royals" by Katie Nicholl.

Prince Harry and Meghan joined William and Kate on a panel at the first annual Royal Foundation Forum in 2018, months after the Duke and Duchess of Sussex announced their engagement in 2017. A source told Nicholl that William and Kate experienced a "wake-up moment" after the event, The Mirror reports.

"The Cambridges had already signalled their intention to be more than 'ornamental royals' and had, along with Harry, made a huge success of their mental health campaign Heads Together," Nicholl, a royal expert, wrote.

The appearance proved that Meghan was more than capable of handling herself well in the spotlight.

"But Meghan was the breakout star of the foursome. She was polished, passionate and funny, using all her TV-honed skills to present her case," according to the book.

Meghan's reception at the event came as a surprise to William and Kate, who had previously been the sole faces of modern royalty.

"'That was a wake-up moment for William and Kate when they realized that Meghan was very impressive, very confident and very capable," according to a source who spoke with Nicholl.

The reported long-standing tension between the brothers began when William expressed concerns about how quickly Meghan and Harry's relationship was progressing. According to Robert Lacey's book "Battle of Brothers: William and Harry — The Inside Story of a Family in Tumult," William worried that Harry was "moving too fast" with Meghan.

In 2020, Harry and Meghan stepped away from their royal duties, which led to "complicated issues" within the royal family, Insider reported.

After Harry and Meghan's explosive interview with Oprah Winfrey in 2021, the distance between Harry and his family widened. During the conversation, Harry claimed that William and their father, King Charles III, were "trapped" in "the Firm," a nickname for the royal family.

According to Us Weekly, Prince William was "fuming" after the interview aired. A source clarified that "William is bound by his duty, but doesn't feel trapped," the outlet reports.

Their feud seemingly came to a halt after Queen Elizabeth died on September 8. The brothers walked side by side and joined their wives at numerous ceremonies honoring their grandmother.

In her book, Nicholl also wrote that William and Kate were relieved when Meghan and Harry stepped down from their royal duties. The couple reportedly felt like the "drama was gone," once they resigned.

According to Nicholl's book, the Queen was "exhausted" by the royal family's issues with Harry and Meghan and wished for the family to reconcile.