It's easy to forget that the bond between King Charles and Harry, his “favorite boy,” was once a source not only of affection but also of joy – a relationship perhaps even warmer than that between Charles and William.
The distance between them has now grown to such an extent that their conversations, where conversations have taken place at all, have become mere echoes of the past.
We saw this vividly in recent days when, upon learning of his father's shock cancer diagnosis, Harry jumped on a plane and flew 5,500 miles to visit him.
It was widely reported that Charles was “touched” by the gesture. Maybe it was him.
But I'm told the reality is both more complex and more disturbing – that Harry caused some disruption by “taking it upon himself” to fly over uninvited and at such short notice.
Prince Harry arrives at Clarence House yesterday to visit his father King Charles after learning of the shock cancer diagnosis
King Charles and Queen Camilla leave Clarence House yesterday, a day after his cancer diagnosis was announced
To be clear, the king was unhappy with the fait accompli presented to him by an emotional but well-meaning son.
Charles simply needs peace and quiet now and had planned much earlier to fly to the tranquility of Norfolk with his wife, the Queen, on Tuesday.
But thanks to Harry's intervention, Their Majesties remained behind at Clarence House, their primary residence in London, while they awaited the appearance of their lost younger son.
It is notable that Harry was not invited to stay at Clarence House or any other royal residence. The decision to fly came so late that he had to book a hotel room for the night.
And if the prince had expected to spend some “quality time” at Sandringham House, perhaps talking about the good old days or re-building the paternal bond, he would have been disappointed.
To be clear, the king was unhappy with the fait accompli presented to him by an emotional but well-meaning son.
What was actually said between them is known only to His Majesty the Queen and the Duke of Sussex, but half an hour (I was told it was a 30 minute meeting, not even 45) was hardly enough to cover that Many bridges have been reduced to ashes.
Not after all this vilification of the royal family, all the misrepresentation that Montecito pours out for a fistful of dollars.
After barely having time for a greeting kiss and perhaps a hug, the king headed with the queen to Buckingham Palace to board the monarch's Sikorsjy S-76C helicopter.
I can't blame Harry for flying over. However reassuring the palace courtiers may sound, his father's diagnosis is a serious matter.
However, the Prince should also spend some time reflecting on the stress he has caused the King, not least as he dealt with the loss of first his own father, Prince Philip, and then of course his late mother, the Queen.
Who could be surprised if Harry wasn't welcomed with open arms?
Although this spontaneous visit was well-intentioned, it was a sad reminder of the ongoing rift within the family, a burden that Charles can ill afford in his current state as he must focus all his energy on the challenge of his health.
There is also a question of trust, or lack thereof.
The prince finds himself in a situation where even those closest to him in the royal family have to be on guard. This is inevitably the case.
It's as if everything ever said between father and son, especially in the painful later years, has been revealed – first in Harry and Meghan's painful-to-watch Netflix show and then in his excruciating memoir, Spare.
Today, as Prince Harry flies back to California, the exuberant celebrations of his 2018 wedding to Meghan Markle seem a million miles away.
One of the most touching moments came when Charles stood in for Meghan's father Thomas, who was in hospital with a suspected heart attack.
The Duke of Sussex waits at Heathrow Airport today for his flight back to the US after seeing the King
Millions of viewers still remember how Charles – immaculate in a gray buttonhole Anderson & Sheppard morning suit from the garden of his Highgrove estate – smiled at Meghan and gently placed her arm through his as she joined the choir at St George's Chapel approached.
Charles was delighted to welcome Meghan into his family. A moment that could have been awkward was endearing. Almost shaking with tension, Harry had turned to his father and whispered “Thanks, Pa” – a sign of the raw love between the two.
That evening, guests went outside to watch a spectacular fireworks display that lit up the darkness over Windsor Castle.
“Who pays for that?” Charles half-jokingly asked one of the guests from the royal household, who replied: “I think so, sir.”
He just laughed.
Four days later, we saw the warmth between father and son show itself again – and in an even warmer way.
This was the occasion for the “Patron Celebration for the 70th Birthday of the Prince of Wales” at Buckingham Palace with around 6,000 guests from Charles's 400 patronages and military associations.
Inevitably, photographers focused on the new Duchess of Sussex, immaculate in a silk crepe pencil dress and Philip Treacy dome hat. This was her first official engagement since her marriage.
But Harry also played his part and gave a speech full of self-irony and warm warmth towards his father.
“Pa,” he said, “even though I know you asked that today not be about you, you have to forgive me if I don't listen to you.” Similar to when I was younger.
Instead, I ask everyone here to say a big thank you for your incredible work over almost 50 years.”
He continued: “It is your selfless drive to create change, whether to improve the lives of those on the wrong path… or to protect a particular endangered species, that William and I are inspired by every day .”
This appears to have been the height of affection between Charles and Harry.
Riots against the royal family followed, taking their toll on both Charles and the late Queen, who found the experience tiring.
But amid the chaos, there are still some glimmers of hope. For example, I am sure that the king still has a soft spot for his younger son, with whom he once spent hours discussing, among other things, the environment and sustainability.
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Despite his own difficulties, and perhaps against his better judgement, Charles has extended plenty of olive branches and will continue to do so.
His generosity knows no bounds, even when his efforts seemed to fall on deaf ears. Until now.
Perhaps Harry is beginning to see more clearly: his father is, after all, only human, a man who has always been there for his son and who won't be there forever.
And Wilhelm? The fact that his brother accused him of bullying is bad enough, but I know he sees Meghan and Harry's attacks on his wife as unforgivable.
Real, raw emotions have fueled discord on both sides, while Catherine, Princess of Wales's recent health problems have only complicated matters.
But with their father undergoing cancer treatment, the responsibility now surely falls on the brothers to make amends – and perhaps on one brother in particular. Because I believe that William could be the key to the solution.
While swallowing his pride is no easy task – and I accept that the Prince of Wales finds it more difficult than most – a certain generosity from the older brother may well be the only way out, both for the good of his family and the Nation family.
Perhaps with hope and perseverance the broken bonds can still be mended and harmony restored.
In his ghost-written memoir Spare, Harry recalls a moment after Prince Philip's funeral at Windsor Castle in March 2021.
By this time Charles had stood between his sons, his face flushed, and said, “Please boys. Don't make my final years a misery.”
Surely it is time for the princes to heed these words.
After all King Charles has done for them both, one would think it would be the least they could do for their father in this hour of need.
Robert Jobson is the author of the bestselling book Our King: Charles III – The Man and The Monarch Revealed.