SARAH VINE: In these turbulent, frightening times, this is a shock and a blow to all of us. Get well soon, Your Majesty. Your country needs you…

When the king left hospital last week, he seemed in good spirits. Sure, he seemed a little frail, leaning somewhat gingerly on the trunk of his car as he walked around it – but he had just completed a rather delicate operation.

But as he greeted well-wishers on his way to church in Sandringham on Sunday, he looked slightly less cheerful. Maybe it was just my impression, but it looked like he had lost weight; his signature double-breasted camel coat was a little loose and his face pale and haggard. Did he just need some time to recover? Or was there more going on?

Unfortunately, we now know it is the latter. Although the King's procedure to treat an enlarged prostate was successful, medics have identified a new problem that requires urgent treatment, which will put him out of action for the foreseeable future.

This inevitably comes as an unwanted shock, not only to the nation, which is still very much in mourning after the death of his mother, but also to the royal family itself, which is only just getting back on its feet after a truly terrible, painful few years.

There is a bright spot: for all intents and purposes, this problem was discovered early and should therefore respond well to treatment. Still, of all the challenges the king could have faced in the first eighteen months of his new reign, this is perhaps the least expected.

For while it is true that he came to the throne as the oldest person to ever accede to the British crown (as well as being the longest-serving Prince of Wales in history), he has always had poor health and – like his mother – led a scrupulously healthy, active lifestyle.

And despite being 75, that's nothing by the Winsdors' standards. Both his parents remained active well into their 90s, and his grandmother, the Queen Mother, was 101 when she died.

Until last week he was even planning to go skiing with old friends in the Swiss Alps, as he has enjoyed doing for years. That trip, as well as several other official ones, has now been canceled while he undergoes further treatment for this unspecified new problem.

It's a big blow. Not just for the royal family themselves, and especially for poor Queen Camilla, who undoubtedly has to worry; but for all of us, and especially so soon after the loss of his dear mother, our rock through the decades.

In these terrifying times, when terrible, turbulent events are taking place around the world and at home, one feels more than ever the absence of Her Majesty's calming, reassuring presence.

It doesn't help that the Princess of Wales herself is recovering from surgery for an unspecified illness. She may not be the royal lady who takes on the most official duties (she does have three young children to care for, after all), but her undeniable star quality is priceless. Additionally, Prince William will inevitably feel the need to spend more time with her and their children – which will limit his ability 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 many people's expectations) it all went so well.

Not only was the coronation a triumph, King Charles has somehow managed to deal with the not inconsiderable challenges of dealing with his brother Andrew's ongoing sex scandal and the behavior of his youngest son.

And yet, despite these trials – which also greatly affected the Queen in her final days and months – Charles has begun to shape his own identity as king; an identity based largely on the same principles as those of his late mother – duty, fortitude, kindness, compassion – and deeply respectful of her legacy (as it should be); but framed by his own life experiences and passions.

When he was released from hospital last Monday, the king appeared steadfast as he left the London clinic in Marylebone with Queen Camilla at his side.

Let's not forget: Queen Elizabeth II was a girl queen who grew into the role; he had lived a lifetime before that crown – and that enormous responsibility – was placed on his head. And yet he has carried both admirably so far.

It must be extremely frustrating for him to have to hit the pause button at this early and crucial stage. In fact, I would be so presumptuous as to say that he will be fooling himself, since he is a man who feels his responsibilities keenly. I feel sorry for his doctors: he will be a terrible patient, always taking every opportunity to return to work in the service of the nation. But he needs to rest and recover, and not be too hard on himself.

Because in the short time he has worn the crown, he has already earned the trust and respect of the British people. Recent polls show him with a stable popularity rating of around 70 percent, with many people pleasantly surprised at how well he has settled into his new role. And he has a loyal and loving son in Prince William, an absolute rock in Princess Anne – and a woman in Queen Camilla who would walk over hot coals for him.

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