MAUREEN CALLAHAN: How hard it must have been for Harry to hear the sad news of Charles’s cancer diagnosis from so far away. Now, as he flies home, could this be the start of a heart-warming royal reconciliation?

If ever there was a chance for royal reconciliation, now is the time.

For all of Prince Harry’s publicly expressed doubts that there is no need for him in the royal family, that he is but a ‘spare’ — the deeply concerning news about King Charles III’s cancer diagnosis proves nothing is further from the truth.

Prince Harry is essential to his family, now as never before.

King Charles has said that the door is always open to his youngest son. Now is the perfect time for him to take this opportunity.

It was only a few weeks ago that his sister-in-law, the Princess of Wales, was hospitalized for a two-week stay following abdominal surgery.

This came in tandem with news that Charles would undergo an operation for an enlarged prostate.

The King’s surgery, we now know, revealed cancer in another, unspecified area.

The Palace has declined to give further details, but the hope is that it has been caught early.

For all of Prince Harry ’s publicly expressed doubts that there is no need for him in the royal family , that he is but a ‘spare’ – the deeply concerning news about King Charles III’s cancer diagnosis proves nothing is further from the truth. Prince Harry is essential to his family, now as never before.

King Charles has said that the door is always open to his youngest son. Now is the perfect time for him to take this opportunity.

Yet this newly streamlined monarchy has suffered two major blows, with its most popular royals — a King who has spent a little over a year on the throne and the future Queen, the most glittering star in its constellation — out of commission.

William has cancelled all his engagements to be with Kate as she recovers. Charles, who began treatment on Monday, has cleared his calendar. Surely Camilla will be by his side in the days and weeks to come.

It’s a dark hour for the monarchy – and doubtless a darker one for Harry.

How difficult it must have been for him to hear this sad news while so far away.

How keenly his absence, and that of little Archie and Lilibet, must be felt back home. Charles has only met Lilibet once, during the late Queen’s Platinum Jubilee celebrations — the only time she met her namesake, too.

‘It was wonderful to have [the grandchildren] back in Britain’, a royal source said at the time, adding that Charles and Camilla ‘were absolutely thrilled to see them’.

The Palace has confirmed that Charles told each of his sons about his diagnosis personally. Harry announced that he is flying home to London immediately.

Will his children soon join him, as the King and Queen would surely hope? One senses that even Meghan might be cautiously welcomed. Charles did, after all, walk her down the aisle.

William, as we know, is less forgiving than his father. But with Kate recuperating, with three small children who need his constant presence, with a sick father and the weight of the Crown suddenly heavier than ever, the absence of his only sibling must be freshly painful.

Could this window, long shut to Harry, be slightly ajar?

What an opportunity this might be. What a comforting presence Harry and his children could provide to the King as he undergoes treatment.

What a gift he and William could give their ailing father if they could find their way to some rapprochement.

Their relationship might never be the same again, of course, but that could be a good thing — or at least, a more honest one.

It’s a dark hour for the monarchy – and doubtless a darker one for Harry. How difficult it must have been for him to hear this sad news while so far away.

What an opportunity this might be. What a comforting presence Harry and his children could provide to the King as he undergoes treatment.

A reconciliation doesn’t mean they have to go deep. If they can find a way to come back together, it would be greater than any title or castle or inheritance — especially for their children, who have no relationship as cousins. And specifically for Harry’s children, who have little relationship to their most incredible and historic lineage.

A brotherly reconciliation would ensure the future of the monarchy itself.

Will Harry now re-find an appreciation for his blood ties to a wounded father who continues to protect him, a brother who shared with him the very public loss of a beloved mother, and, indeed, a sister-in-law he once so openly adored?

Harry failed to make good with the Queen before she died. At the end, he missed his chance to fly to her bedside with William and other family members after reportedly demanding that Meghan accompany him.

One imagines he regrets that.

Harry’s demand left the royals ‘shocked by his behavior’, as Robert Jobson reported in his well-sourced biography, ‘Our King: Charles III’.

Jobson also claimed that stripping Harry of his title had ‘been discussed at the highest level’ with Charles refusing to consider it out of ‘enduring love for his son’.

There has never been a more auspicious moment for a royal reconciliation than right now.

Prince Harry isn’t just needed at this moment. It’s quite clear he is very much wanted.

Let’s hope the self-proclaimed spare recognizes just how important he is — and all that he can be, to his family and his country, if he allows.