King Charles and Catherine, Princess of Wales visits the Grange Pavilion

Kate Middleton’s unique strength is not lost onKing Charles.As she helped the King andQueen Camillahost more than 500 members of the diplomatic corps at the annual Buckingham Palace reception on Dec. 5, the Princess of Wales, 41,worked the room, glittering in the historic Lover’s Knot tiara.“She hugely enjoyed that evening and looked really at home,” a royal source tells PEOPLE in this week’s issue. “She knows the important role the family plays in building relationships globally on behalf of the U.K.” Adds the insider: “It is clear that she and the King are quite close — in some respects closer to him than William.“Noting Prince William andPrince Harry’s “fractious relationship” with their father, the insider says, “It’s only been recently that William hasbeen closer[to Charles] — and Kate has acted as the honest broker in that.“Queen Camilla, King Charles, Prince William and Kate Middleton, Princess of Wales at Buckingham Palace on Dec. 5, 2023.Chris Jackson/GettyLike other royal consorts in history, Kate has developed a toughness behind the scenes as she supports her husband and future king William. “She has this public image of being nice and smiley and, dare I say, innocuous,” royal author Valentine Low tells PEOPLE. “But she is actually strong-minded, strong-willed and prepared to fight for what she wants and what she thinks is right.”Of her role alongside her husband, a former staffer says, “She provides William with “directional setting. She guides the family and guides him.” Adds royal biographer Sally Bedell Smith: “They are pursuing the initiatives that are important to them. They are not pushing to supplant the King and Camilla—they are an incredible enhancement.”Kate’s steeliness came into play in the immediate aftermath of Harry andMeghan Markle’s bombshell interview withOprah Winfreyin 2021. After the Duke and Duchess of Sussex alleged that there were “concerns and conversations about how dark” their sonPrince Archie’s “skin might be when he’s born,” Buckingham Palace released a 61-word statement on behalf ofQueen Elizabeth.Prince William, Kate Middleton, Prince Harry and Meghan Markle at the annual Commonwealth Service at Westminster Abbey in March 2020.PHIL HARRIS/POOL/AFPThe statement pointedly noted that “some recollections may vary” regarding what was discussed in the interview — and Low writes in his bookCourtiers: The Hidden Power Behind the Crown(out in paperback in September) that Kate played a key role in pushing that phrasing.“She thought it was very important this did not go unchallenged. She showed real strength and determination to make things clear that there was perhaps a different truth,” Low says. “Kate thinks strategically,” he adds. “She is going to be queen one day and has the longterm interests of the monarchy and royal family at heart.”Kate Middleton and Prince William arrive to attend the Royal Variety Performance in London on Nov. 30.DANIEL LEAL/AFP via GettyCan’t get enough of PEOPLE’s Royals coverage?Sign up for our free Royals newsletterto get the latest updates on Kate Middleton, Meghan Markle and more!“She takes things seriously — and thank goodness for that,” says a source close to the royal household.Adds Simon Lewis, former Buckingham Palace communications chief and cohost of the BBC podcastWhen It Hits the Fan, “She’s very much seen as a player at the center of team Windsor.”

Kate Middleton’s unique strength is not lost onKing Charles.

As she helped the King andQueen Camillahost more than 500 members of the diplomatic corps at the annual Buckingham Palace reception on Dec. 5, the Princess of Wales, 41,worked the room, glittering in the historic Lover’s Knot tiara.

“She hugely enjoyed that evening and looked really at home,” a royal source tells PEOPLE in this week’s issue. “She knows the important role the family plays in building relationships globally on behalf of the U.K.” Adds the insider: “It is clear that she and the King are quite close — in some respects closer to him than William.”

Noting Prince William andPrince Harry’s “fractious relationship” with their father, the insider says, “It’s only been recently that William hasbeen closer[to Charles] — and Kate has acted as the honest broker in that.”

Queen Camilla, King Charles, Prince William and Kate Middleton, Princess of Wales at Buckingham Palace on Dec. 5, 2023.Chris Jackson/Getty

Queen Camilla, King Charles III, Prince William, Prince of Wales and Catherine, Princess of Wales pose for a photograph ahead of The Diplomatic Reception in the 1844 Room at Buckingham Palace on December 05, 2023 in London, England.

Chris Jackson/Getty

Like other royal consorts in history, Kate has developed a toughness behind the scenes as she supports her husband and future king William. “She has this public image of being nice and smiley and, dare I say, innocuous,” royal author Valentine Low tells PEOPLE. “But she is actually strong-minded, strong-willed and prepared to fight for what she wants and what she thinks is right.”

Of her role alongside her husband, a former staffer says, “She provides William with “directional setting. She guides the family and guides him.” Adds royal biographer Sally Bedell Smith: “They are pursuing the initiatives that are important to them. They are not pushing to supplant the King and Camilla—they are an incredible enhancement.”

Kate’s steeliness came into play in the immediate aftermath of Harry andMeghan Markle’s bombshell interview withOprah Winfreyin 2021. After the Duke and Duchess of Sussex alleged that there were “concerns and conversations about how dark” their sonPrince Archie’s “skin might be when he’s born,” Buckingham Palace released a 61-word statement on behalf ofQueen Elizabeth.

Prince William, Kate Middleton, Prince Harry and Meghan Markle at the annual Commonwealth Service at Westminster Abbey in March 2020.PHIL HARRIS/POOL/AFP

Britain’s Prince Harry, Duke of Sussex, (2nd R) and Britain’s Meghan, Duchess of Sussex (R) sit behind Britain’s Prince William (L), Duke of Cambridge and Britain’s Catherine, Duchess of Cambridge (2nd L) inside Westminster Abbey as they attend the annual Commonwealth Service in London on March 9, 2020. - Britain’s Queen Elizabeth II has been the Head of the Commonwealth throughout her reign. Organised by the Royal Commonwealth Society, the Service is the largest annual inter-faith gathering in the United Kingdom. (Photo by Phil HARRIS / POOL / AFP) (Photo by PHIL HARRIS/POOL/AFP via Getty Images)

The statement pointedly noted that “some recollections may vary” regarding what was discussed in the interview — and Low writes in his bookCourtiers: The Hidden Power Behind the Crown(out in paperback in September) that Kate played a key role in pushing that phrasing.

“She thought it was very important this did not go unchallenged. She showed real strength and determination to make things clear that there was perhaps a different truth,” Low says. “Kate thinks strategically," he adds. “She is going to be queen one day and has the longterm interests of the monarchy and royal family at heart.”

Kate Middleton and Prince William arrive to attend the Royal Variety Performance in London on Nov. 30.DANIEL LEAL/AFP via Getty

Britain’s Catherine, Princess of Wales and Britain’s Prince William, Prince of Wales arrive to attend the Royal Variety Performance at the Royal Albert Hall in London on November 30, 2023.

DANIEL LEAL/AFP via Getty

Can’t get enough of PEOPLE’s Royals coverage?Sign up for our free Royals newsletterto get the latest updates on Kate Middleton, Meghan Markle and more!

“She takes things seriously — and thank goodness for that,” says a source close to the royal household.

Adds Simon Lewis, former Buckingham Palace communications chief and cohost of the BBC podcastWhen It Hits the Fan, “She’s very much seen as a player at the center of team Windsor.”

source: people.com