Sarah Vine: King Charles’ cancer diagnosis is a shock and blow for us all

When the King left hospital last week, he looked to be in cheery spirits.

Sure, he seemed a little fragile, leaning somewhat gingerly on the boot of his car as he walked around it – but then he had just had quite a delicate operation.

On Sunday, however, as he greeted well-wishers on his way to church at Sandringham, he looked a little less chipper.

Perhaps it was just my impression, but he seemed to have lost weight, his trademark double-breasted camel coat a little loose on him, his face pale and drawn.

Was he just taking a bit of time to recover? Or was there something more going on?

Sadly, we now know it’s the latter. While the King’s procedure to treat an enlarged prostate was successful, the medics have identified a new problem which will require urgent treatment, putting him out of action for the foreseeable future.

Inevitably, this comes as an unwelcome shock, not just for the nation, still very much in mourning after the death of his mother, but also for the royal family itself, which has only just been getting back on its feet after a really horrible, painful few years.

There is a silver lining: By all accounts this problem has been identified early and should therefore respond well to treatment.

Still, of all the challenges that could have faced the King in the first 18 months of his new reign, this is perhaps the least expected.

Because while it’s true that he came to the throne as the oldest person ever to accede to the British crown (having also been the longest-serving Prince of Wales in history), he has always been in rude health, leading – like his mother – a scrupulously wholesome, active lifestyle.

And despite being 75, by the standards of the Winsdors that’s nothing. Both his parents remained active well into their nineties, and his grandmother, the Queen Mother, was 101 when she died.

Indeed, until last week he was planning to go skiing – as he has done with gusto for many years – with old friends in the Swiss Alps.

That trip, as well as several other official ones, has now been cancelled while he undergoes further treatment for this unspecified new problem.

It’s quite a blow. Not only to the Royal Family themselves, and in particular to poor Queen Camilla, who must be worried sick; but to us all, and especially so soon after the loss of his dear mother, our rock throughout the decades.

In these anxiety-inducing times, with terrible, turbulent events taking place all over the world and at home, one feels more than ever the absence of Her late Majesty’s calming, reassuring presence.

It also doesn’t help that the Princess of Wales is herself convalescing after an operation for an unspecified illness.

She may not be the royal who racks up the most official engagements (after all, she does have three young children to care for), but her undeniable star quality is an invaluable asset.

Plus Prince William will inevitably feel the need to spend more time with her and their children – which will make him less able to take on some of his father’s duties while he recovers.

But what really makes this latest setback so frustrating is the fact that (against the expectations of many) it was all going so well.

Not only was the Coronation a triumph, King Charles has somehow managed to navigate the not inconsiderable challenges of dealing with his brother Andrew’s ongoing sex scandal and his youngest son’s behaviour with almost zen-like calm and fortitude.

And yet despite these tribulations – which also greatly afflicted the Queen in her final days and months – Charles has begun to carve out his own identity as King; an identity built very much on the same principles as those of his late mother – duty, constancy, kindness, compassion – and deeply respectful of her legacy (as it should be); but framed by his own life experiences and passions.

Let’s not forget: Queen Elizabeth II was a girl queen who grew into the role; he had lived a whole life before that crown – and that immense responsibility – was placed on his head. And yet, so far, he has borne both admirably.

To have to press the pause button on all that at this early and crucial stage must be extremely frustrating for him. In fact, I would be so presumptuous as to say he will be kicking himself, since he is a man who feels his responsibilities acutely. I pity his doctors: He will make a terrible patient, always pushing at every opportunity to get back to work in the service of the nation.

But he must rest and recuperate, and not be too hard on himself.

For in the short time that he has worn the crown he has already earned the trust and respect of the British people.

Recent polling shows he has a steady popularity rating of around 70 per cent, with many people being pleasantly surprised at how well he has settled into his new role.

And he has in Prince William a loyal and loving son, in Princess Anne an absolute rock – and in Queen Camilla a woman who would walk over hot coals for him.

Let them take up the slack for now. And get well soon, your Majesty. Your country needs you.