What does the King's diagnosis mean for William, Harry and the other royals?

It all began three weeks ago, entirely out of the blue on an icy cold January afternoon, with a message that Catherine, the Princess of Wales, had had an operation serious enough to require months of recovery.

Barely had the TV cameras scrambled to her hospital in London, when it was also announced that the King was going to have a procedure for an enlarged prostate.

It was an entirely unexpected double royal health blow that was then compounded by Sarah Ferguson, Duchess of York, revealing she had skin cancer.

Now we learn that the King has a form of cancer. All the questions that get asked by families everywhere on getting such troubling news - Where? How far? What type? What next? - remain unanswered.

Royal information may be put out by palaces on social media these days, rather than anything more ceremonial. But however it arrives, it's been a torrent of bad news for the royals. The Royal Family is still a family after all.

And it looks a much more fragile group of people than it did in the summery celebrations of last year's Coronation.

But such emergencies can pull people together.

Without any equivocation or complication, Prince Harry is coming to visit his father, travelling over from the US alone in the next few days.

It will be seen as building bridges but that was already in process, with the prince calling his father for his 75th birthday in the autumn. The tension always seemed to be more with his brother and the tabloid press, rather than his father.

Prince William, who was already due to return to official duties after his wife's operation, will now be expected to play a bigger role in terms of public appearances and covering for official duties. But he faces both his wife and father as being ill at the same time.

But Prince William is the heir, the next in line, and will be expected to step up, in the way that not that long ago, King Charles was stepping up to help his own mother. Attention will turn to him when he appears publicly later this week.

He will be worrying about his wife's health problems. But the palaces will also miss Catherine, as one of their most reliable figures in troubled moments, and now out of action for months.

Queen Camilla, who 20 years ago wasn't even part of the Royal Family, has continued her remarkable journey in from the cold.

She's now centre stage, carrying out a series of solo engagements last week, as a senior member of a shrinking group of working royals.

It seems a long time since there were debates about "slimming down" the monarchy, with Prince Harry and Prince Andrew having stepped down and now the King and the Princess of Wales out of action.

Among the working royals, only the Prince and Princess of Wales are aged under 50. The group seems to have become older and more frail.

For the King himself, at the eye of this storm, he will carry on with the duties of head of state, keeping up the paperwork and the red boxes of ministerial documents and the private meetings.

But it will mean missing the part of the job that really seems to energise him, because the King seems to be at his most enthusiastic when he meets the crowds. There's a remarkable lack of pomposity or formality on such trips when he goes out to meet the public.

After meeting the local worthies and unveiling plaques on visits, he always seems relieved to head into the crowds outside.

That will be on pause - although for how long, we don't know. Because once again this is a reminder that although we see so much of the royals, there is so much we don't know.

There was a spirit of openness in announcing that the King was to have a prostate procedure, which was intended to raise awareness and encourage more men to get checked - and similarly in the sharing of his cancer diagnosis.

But it's a guarded openness, pushing the palace door ajar a little. What happens next remains unknown.

-bbc