Harry’s arrival will test William’s resolve. So will their father’s illness lead to a rapprochement between brothers?

It is not difficult to imagine the confusion of emotions that will be running through Prince William’s mind today: sadness and anguish at his father’s illness, but also bewilderment at the scale of the challenge he now faces and the inevitable sacrifices he will be forced to make.

The parallels with what his beloved grandmother faced more than 70 years ago are striking. The then Princess Elizabeth was 25 and a young mother when she so unexpectedly succeeded her father as monarch.

She and Prince Philip had every reason to hope that they had a good ten years of family life ahead of them before the responsibility of the throne intervened.

William is 16 years older than his grandmother was at that crucial moment and his children are older, but his sense of anticipation for the future would not have been less.

And while he’s not about to become king, his life is about to change in every other way.

Old guard: Charles and Camilla lead William, Kate, Harry and Meghan at Commonwealth Service in London in 2020

Old guard: Charles and Camilla lead William, Kate, Harry and Meghan at Commonwealth Service in London in 2020

Prince Harry and William are believed not to have exchanged a word for many months, their relationship apparently shattered by Harry's memoir, Spare

Prince Harry and William are believed not to have exchanged a word for many months, their relationship apparently shattered by Harry’s memoir, Spare

Following the news of King Charles' cancer diagnosis, it is not clear how much of his father's schedule will now carry over to the prince

Following the news of King Charles’ cancer diagnosis, it’s not clear how much of his father’s schedule will now carry over to the prince

Suddenly, all of his and Kate’s carefully thought-out plans, in which their children’s welfare was the priority, now seem vulnerable. What makes the uncertainty all the greater is the unforgiving nature of the King’s condition.

Life in the goldfishbowl of the royal family could never have felt quite so lonely or so dangerous. For William, the pressure is doubly intense, because the extra burden that will come while his father is undergoing treatment for cancer will have to be faced alone.

It is just eight days since Kate was released from hospital, where she underwent abdominal surgery, and she is not expected to resume public duties until after Easter. William himself is due to return to work tomorrow, having canceled all engagements to look after George, Charlotte and Louis.

How much of his father’s schedule will now carry over to the Prince is not clear. But the news that he will be performing comes with an added distraction – Prince Harry’s decision to rush to his father’s side.

While it was unthinkable that Harry would not want to fly to Britain once bulletins about Charles were issued, his presence will serve as a reminder of how fractured the royal family has become since Queen Elizabeth’s death in 2022.

It will be the first time he has seen his father since the Coronation in May last year. To the relief of courtiers, the Duke of Sussex will apparently make the trip without his wife Meghan. The question is: is he going to see William too?

The brothers are believed not to have exchanged a word for many months, their relationship apparently shattered by Harry’s memoir, Spare. In the book, published a year ago, Harry accused William of physically attacking him, and Kate of being cold towards Meghan.

As he grapples with his new responsibilities, William’s thoughts will almost certainly turn to how his grandmother would have handled such a princely invasion.

King Charles' diagnosis also means that all of William and Kate's carefully thought-out plans, in which their children's welfare was the priority, suddenly look vulnerable again

King Charles’ diagnosis also means that all of William and Kate’s carefully thought-out plans, in which their children’s welfare was the priority, suddenly now look vulnerable

The Duke of Sussex is thought to be making the trip to see his father without his wife Meghan

The Duke of Sussex is thought to be making the trip to see his father without his wife Meghan

He can also draw some strength from the dignity with which the late queen faced her fate all those decades ago. She obviously did it from a position of strength.

Public affection for her father, King George VI, for the way he led the nation through the Abdication Upheaval and the dark days of World War II ran deep when she came to the throne in 1952. William emerges with the monarchy in crisis.

It hasn’t even been two years since he and Kate made the adjustment to their lives that he hoped would pave the way for a new royal lifestyle.

Their move from London to Windsor was not only about allowing all three of their children to attend the same day school, but also about ensuring them a level of privacy that was never quite possible while based at Kensington Palace was not

But the couple’s elevation to Prince and Princess of Wales put this rural idyll under pressure. ‘They have a very cozy life down there at Adelaide Cottage in Windsor Great Park, but it takes a lot of moving parts to work well,’ says a friend.

Their staff are still based in London and meetings often have to take place at Windsor Castle.

The contrast between father and son as Princes of Wales could not be greater. While Charles – like William – is passionate about what he believes in, he was also a lobbyist by nature. William is not. He has his core interests — homelessness, mental health and conservation — but doesn’t spread himself thin like his father once did. For example, William has no interests in the arts.

But, for now at least, William is going to have to cover a lot more ground than he usually prefers. He is almost certain to assume his father’s role in receiving incoming and outgoing foreign diplomats.

So how is he going to pull it off? And, more importantly, what does this change in his status mean for his relationship with Harry?

Certainly, friends say, William has the makings to be dynamic, and some believe taking on these additional responsibilities could be his making, raising both his profile and his visibility.

For starters, William enjoys one quality his father had to wait years for – public affection. From Princess Diana, William inherited natural warmth and a confidence that is complemented by Kate’s unassuming approach.

Even when they were accused of being ‘tone deaf’ about their Caribbean tour to Belize, Jamaica and the Bahamas, criticism of the couple soon died down.

Unlike Charles, who was aware of his future from an early age – he was three years in the line of succession – William was shielded from his fate for years.

“He really had no idea until he went to school,” says a former aide. By the time he was at Eton, the Queen had begun schooling him in the traditions and history of the monarchy over tea in Windsor.

Still, he put off the inevitable as long as he could. After university and military service, he became an RAF search and rescue pilot, later transferring to a civilian role with the air ambulance service.

It is in his approach to fatherhood that he differed so much from the King. While Charles fit the arrival of his sons around his famously busy schedule, William put family life first.

This is surely the influence of Kate’s family. In the Middletons, William found how rewarding family life could be.

He will hope that in time his father’s recovery will allow a partial return to those days of domestic happiness which many believe will make him a modern and well-rounded sovereign.

However, there are two family issues that could determine that assessment: Andrew and Harry. On Prince Andrew, he strongly supported his father’s position that the Duke of York cannot return to frontline royal duties.

But as for Harry, his view diverged from the King’s. While Charles is torn by the conflict between his sons and yearns for a rapprochement, William is convinced that trust, the basis of any relationship, has been totally destroyed.

Harry’s arrival will test William’s resolve. Will he agree to see him, and in time agree to a rapprochement as his father surely wants? Or will the status quo remain?

Charles’ illness and his recovery may determine that outcome.