Kate Middleton 'worried' after King Charles' cancer forces Prince William back to work: author

Princess Kate Middleton is said to be worried about her husband, Prince William, who put on a brave face this week as he carried out royal duties.

On Wednesday night, the Prince of Wales expressed his gratitude to well-wishers at London’s Air Ambulance Charity Gala Dinner. It marked the 41-year-old’s first day back to public engagements in nearly a month following the royal family’s health battles.

As the Princess of Wales is recovering from abdominal surgery, William's father, King Charles III, is receiving treatment for cancer.

PRINCE WILLIAM BREAKS SILENCE ON KING CHARLES' CANCER DIAGNOSIS AT GALA WITH TOM CRUISE

"Kate is worried about the psychic toll these twin medical battles are having on her husband," Christopher Andersen, author of "The King," told Fox News Digital.

"William is terribly concerned about Kate’s condition – we still don’t know what her abdominal surgery was for or why her recovery is taking months – and now he has to face the fact that his father has cancer," Andersen said. "William has always made it clear that he wanted a full-fledged family life, and when Kate became incapacitated, he stepped in to play hands-on dad. He cut back on his schedule to drive the kids to school, the whole nine yards."

"Now he has resumed his royal duties much sooner than perhaps he would have liked," Andersen said. "But there are times when duty trumps family life and, after all, William is the future king."

Patricia Spruce, who works for the NHS (National Health Service), took to LinkedIn and wrote about her experience attending the gala. She said that, according to the father of three, the princess has two nurses looking after her and "they were amazing and kind."

The 42-year-old has been recuperating at the family’s Adelaide Cottage in Windsor.

On Jan. 17, the palace revealed the princess underwent "planned abdominal surgery" at The London Clinic the previous day.

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"The surgery was successful, and it is expected that she will remain in hospital for 10 to 14 days before returning home to continue her recovery," a palace statement said at the time. "Based on the current medical advice, she is unlikely to return to public duties until after Easter."

The palace later noted the royal "is making good progress."

It is unclear why the princess needed abdominal surgery. While it is somewhat unusual for members of the royal family to release details about their health, the initial announcement was likely made to avoid speculation about whether events featuring Princess Kate had to be postponed or canceled over the coming weeks.

On Monday, Buckingham Palace announced the king was diagnosed with a form of cancer and has begun treatment. The palace didn’t say what form of cancer the British monarch has but noted it’s not related to his recent treatment for a benign prostate condition.

The palace said "a separate issue of concern was noted" during Charles’ treatment for an enlarged prostate last month when he spent three nights at The London Clinic.

"Diagnostic tests have identified a form of cancer," the palace said in a statement.

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Charles, 75, ascended to the throne upon the death of his mother, Queen Elizabeth II. England’s longest-reigning monarch died in 2022 at age 96.

Andersen said the king and his "beloved daughter-in-law," as he once referred to her, have maintained a close-knit bond. On the day that Charles was admitted to treat his enlarged prostate, he visited Princess Kate, who was staying at the same hospital, before his procedure.

"Even though Queen Camilla and Kate have always had a frosty relationship, Kate and the king have always been fond of each other," Andersen said. "Charles credits Kate with keeping William grounded, and he knows what a pillar of support she is as well. Kate, in turn, knows that William has immense respect for his father and that there is an incredibly strong bond between the two men – the monarch and the son who will succeed him."

"Certainly no one wants to be reminded of a parent’s mortality," Andersen continued. "But in William’s case, the prospect of losing this parent means that William becomes king and assumes the crushing responsibilities that the job entails. Apparently, Kate and Charles have spoken over the phone, offering each other encouragement. The coincidence of them both landing in the hospital at the same time and having to see it broadcast around the world – well, it’s a weird kind of bonding experience."

British royal expert Ian Pelham Turner told Fox News that the "strong bond" between Princess Kate and Charles has been well-documented over the years and with good reason.

"She has brought new values to the monarchy with her hard work and winning ways with many of the British public," he explained.

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"Prince William has much to process, a lot more work down the line as he takes the weight of the monarchy on his shoulders, taking the pressure off King Charles and looking after his family. … Will William be coerced … [by] Kate to heal the rift with [Prince] Harry? The jury is out on that one, but like with all the royal surprises, never say never."

Prince Harry, William’s younger brother, made a whirlwind trip from California to London to see his father. His visit came shortly after Buckingham Palace announced the king’s cancer diagnosis.

A source told Fox News Digital that the Duke of Sussex, 39, had previous communication with his father before the news of his illness went public.

"The duke did speak with his father about his diagnosis," the source confirmed.

The Duke of Sussex spent about 24 hours in the U.K. before catching a flight back home. According to several royal experts, the father and son had a private meeting that lasted for 45 minutes. Allegedly, the brothers didn’t meet and there were no plans to do so.

Harry’s wife, Meghan Markle, stayed behind in California with their two young children.

PRINCE HARRY LEAVES UK AFTER KING CHARLES VISIT WITHOUT MEETING WITH PRINCE WILLIAM

"What makes the whole situation even sadder is that Harry and Kate used to be so close – ‘like the sister I never had,’ he said at William and Kate’s wedding reception," said Andersen. "Harry must also be extremely concerned about his sister-in-law, but it’s highly doubtful that William would want him anywhere near her now."

In 2020, the Duke and Duchess of Sussex stepped back as senior royals and moved to California. At the time, they alleged palace officials were insensitive to Markle’s mental health struggles as she attempted to navigate royal life. The couple also alleged that the duchess faced racist attitudes from the U.K. press, which contributed to their decision to leave the country.

Following their departure, the couple aired their complaints about life as royals. In 2021, they sat down with Oprah Winfrey for an interview that was viewed by 50 million people globally. After releasing a six-part docuseries on Netflix in 2022, Harry’s memoir, "Spare," hit bookshelves in 2023, quickly becoming a bestseller.

The relationship between the brothers, which was strained by the time Harry made his exit, worsened when he publicly detailed his grievances. Harry also discussed his sibling rivalry in his bestselling book.

"Illness has a way of getting family members to put aside petty differences, but that’s not the case here," said Andersen.

"William has refused to meet with Harry and is channeling some of the anxiety about his wife and father into anger – anger directed at his brother," he said. "One might think the two brothers would find a way to bury the hatchet, even if only temporarily, for the king’s sake. It’s entirely conceivable that William simply has too much on his plate to deal with the Harry issue and all it entails.

PRINCE HARRY VISITS KING CHARLES FOLLOWING CANCER DIAGNOSIS BUT ‘NOT MEETING’ WITH PRINCE WILLIAM: EXPERT

"There are so many reasons for all the royals to come together now. If they don’t, it’s just another sign that they never will."

The Associated Press contributed to this report.