SPECIAL REPORT: Kate Middleton's Ready for the Crown – How Prince William's Wife is Fully Prepped to Step Into Her New Role Any Day Now as King Charles Health Declines

Stunning in a dreamy blush confection by Dior – her first time wearing the famed Parisian label – the Princess of Wales was the epitome of chic as she stepped onto the tarmac at the Royal Air Force's Northolt base outside London, July 8, RadarOnline.com can reveal.

Standing alongside husband Prince William, the 43-year-old warmly greeted France's President Emmanuel Macron, 47, and first lady Brigitte Macron, 72, as they deplaned. Hours later, Kate Middleton worked her magic again, this time dazzling in diamonds and a rich red gown from another French designer, Givenchy, at a historic white-tie state dinner at Windsor Castle as she helped King Charles III, 76, and wife Queen Camilla, 78, celebrate France's first official state visit to Britain in 17 years.

Noted a royal source: "It's been a long time since people saw Kate wear a tiara."

To be exact, since 2023, weeks before a shocking cancer diagnosis upended the mom of three's life and brought her priorities into focus.

But bolstered by her strong sense of "duty" to the crown, the source told RadarOnline.com, Middleton was determined to step up for the momentous occasion with her nation's closest neighbor and ally.

Following an uncertain few weeks – she appeared strong and in good spirits at the monarch's official birthday parade, Trooping the Colour, on June 14 before sparking concern when she pulled out of a planned appearance at the Royal Ascot horse races mere hours before it began – she's now back on the world stage and, in many ways, doing better than ever, said the source.

Not least because she's navigating her role on her terms.

"She looked like a queen," said the source, "and she's up for the task."

Sadly, it might not be long until the job is hers. Nearly a year and a half after Charles, too, was diagnosed with an undisclosed form of cancer, the king is still being treated for what he's called a "daunting" disease.

Courtiers have been privately sharing concerns about his prognosis, which remains closely guarded, with even estranged son Prince Harry, 40, admitting to the BBC in his bombshell May interview, "I don't know how much longer my father has."

Middleton "knows the day is coming," said the source, confirming that she's been taking her responsibilities more seriously than ever during these uncertain times.

Though she acutely feels the gravity of her future, the insider added, this is also "something she’s been preparing for since she got together with William" 23 years ago when they were students at Scotland's University of St Andrews.

At the same time, 14 years into their marriage and six months after announcing she's in remission, there has been a shift.

"As dedicated and committed to her work as she is, her health will continue to come first," said the source. "She is mindful about her well-being and will continue to assess her return to royal duties on a case-by-case basis."

In recent weeks, Middleton has grown uncharacteristically candid about her journey, which marks a major change from how she handled things initially.

Following what Kensington Palace described as a "planned abdominal surgery" at the start of 2024, the future queen learned she had cancer – but she and William, 43, chose to keep her diagnosis a secret for months, fueling harmful speculation about her mysterious absence from the spotlight.

"Kate must realize that staying silent for so long was not the best way to handle the situation," said the source. "But it was traumatic, and she's human, after all. She was processing it herself and didn't want to worry her children," Prince George, who turns 12 on July 22, Princess Charlotte, 9, and 7-year-old Prince Louis.

This new vulnerability is a step toward modernizing the monarchy, making the future queen more relatable than her predecessors.

She showed as much during a July visit to Colchester Hospital in Essex, England.

"You have to find your new normal and that takes time ... and it’s a roller coaster," she confessed. "It’s not smooth, like you expect it to be. But the reality is you go through hard times."

As she spoke with patients about her health-care crisis, she admitted,

"You put on a sort of brave face, stoicism through treatment. Treatment's done, then it's like, 'I can crack on, get back to normal,' but actually the phase afterwards is really, really difficult."

Post-care, survivors often struggle to "function normally at home," she acknowledged, following such a "life-changing" ordeal for themselves and their loved ones.

Indeed, last November, William called 2024 "brutal" and "the hardest year in my life."

Moving forward, one of the most difficult issues hanging over William's future as sovereign, and Middleton as his queen, is his ongoing feud with Harry, which began well before the Duke of Sussex and wife Meghan Markle, 43, left the royal family in 2020 to start a new life in California.

They blamed attacks by the U.K. press, the couple have claimed, were sanctioned and fueled by palace courtiers with the tacit support of Harry’s own family.

"Kate is deeply troubled by William's ongoing rift with his brother," claimed the source.

As RadarOnline.com and other outlets have previously reported, William has privately threatened to strip them – and likely their children, Archie, 6, and Lilibet, 4 – of their Royal Highness titles once he’s king.

Middleton's hardly happy the Sussexes have criticized her and William by detailing private conversations and arguments in interviews, a 2022 Netflix series, and Harry's 2023 memoir, Spare.

But, like Harry, who in May said in an interview, "I would love reconciliation with my family. There's no point in continuing to fight anymore," Middleton, too, thinks peace is best for The Firm.

"Persuading William to let go of grudges has been daunting," said the source, "but she's aware she’s the only one in the royal family who can possibly do it."