A soul-crushing picture of the Royals in peril: Disgraced Andrew given star billing as Kate and Charles recover... Wills goes missing... and Harry and Meghan sulk in Montecito. MAUREEN CALLAHAN asks: How DOES the monarchy come back from this?

The slimmed-down monarchy that King Charles so longed for is now, quite quickly, in crisis.

The absence of Prince William at Tuesday’s memorial service for his godfather, King Constantine of Greece — announced just 46 minutes prior to William’s scheduled arrival — sheds a blinding light on this unfolding catastrophe.

Charles is undergoing treatment for cancer. The Princess of Wales is recovering from abdominal surgery and is not expected to resume public appearances until at least after Easter.

It has been left to William to carry the mantle, but his sudden withdrawal from Constantine’s service, for unknown ‘personal reasons’, is a further crack.

What’s more, it is understood that William’s absence had nothing to do with the sudden death of Tom Kingston, the 45-year-old husband of Lady Gabriella Windsor (Charles’s second cousin), announced just hours later.

Without William’s expected attendance, a hole has been blown wide open in the House of Windsor.

Charles is undergoing treatment for cancer. The Princess of Wales is recovering from abdominal surgery. It has been left to William to carry the mantle, but his sudden withdrawal from King Constantine’s service, for unknown ‘personal reasons’, is a further crack.

Without William’s expected attendance, a hole has been blown wide open in the House of Windsor.

It’s one thing for Charles to be out of commission, and not at all unexpected. He is an older man dealing with health issues.

Kate’s absence, however, is more keenly felt.

She is indisputably the most charismatic and glamorous member of The Firm. William, for all his dignified and cheerful dutifulness, simply seems dulled without her.

It is Kate who gives William true glamour. It is Kate, more than her husband or any other royal, who signifies youth and futurism.

And with William on modified duty, the monarchy not only feels rusty and dusty — it feels imperiled.

Look no further than the disgraced Prince Andrew, apparently viewing this sudden power vacuum as an opportunity to emerge from banishment and lead the royal family – or what was left of it – into Tuesday’s memorial service. Jeffrey Epstein and sex scandal payoffs be damned.

How could Charles allow this?

In the wake of those recent reports that the prodigal Prince Harry was seeking a way back into the royal fold, and that there was a faction in the palace open to reconciliation, it renders Charles soft.

Too soft, perhaps, and too hopeful.

If only Harry and Meghan weren’t the ingrates they are. If only they weren’t so resentful and distrustful.

If only they had stayed put, serving the Crown and doing everything to ensure the future of the monarchy. They would have had the full faith of the British people, who would have embraced them as never before.

For Harry and Meghan, their time would have been now. They would have been front and center, the understudies called up to the lead roles, taking the place of the Waleses as they navigate Kate’s recovery, Charles’s illness, and the raising of their three children.

Look no further than the disgraced Prince Andrew, apparently viewing this sudden power vacuum as an opportunity to emerge from banishment and lead the royal family - or what was left of it - into Tuesday’s memorial service.

How could Charles allow this? In the wake of those recent reports that the prodigal Prince Harry was seeking a way back into the royal fold, and that there was a faction in the palace open to reconciliation, it renders Charles soft.

If only Harry and Meghan weren’t the ingrates they are. If only they weren’t so resentful and distrustful. Their time would have been now. They would have been front and center, the understudies called up to the lead roles.

Meghan, at long last, would have had her Norma Desmond moment, moving ever closer toward the camera under a permanent white-hot spotlight.

The stage would have been all hers. Alas.

Harry and Meghan’s attempted rebrand in just the past week — that relaunched Sussex website with Meghan’s royal crest and the demand out of Canada, during Harry’s Invictus promotions, that she be called ‘ma’am’, plus Harry’s ‘GMA’ interview in which he spoke about his recent trip to see Charles — remains further proof that all they’ve got left to peddle is their connection to the royals.

A connection that grows more slack by the moment, to the very royalty they paradoxically seek to destroy.

Do Harry and Meghan even realize what they’ve lost? What cost this is to their own children? To the British people?

In an alternate universe, Tuesday’s service would have seen the Duke and Duchess of Sussex leading the way, standard bearers for an intact monarchy, slim but powerful, padded with key players of vim and vigor, style and star power.

Instead, we were made to suffer a shameless Prince Andrew in full cock-of-the-walk, chest thrust forward, smiling broadly, emitting an aura of utter confidence as the royal alpha male.

What an insult to Prince William. What an insult to Princess Anne, trailing behind her besmirched brother. Her sheer workload and devotion to monarchy deserves better.

It was all rather maudlin and colorless, despite Andrew’s beaming white grin — which felt, frankly, completely inappropriate.

Where does this leave the royals? The future of a monarchy dimmed by the loss of Queen Elizabeth and further diminished by the withdrawal, for the moment, of Kate?

Could the dissipation of the once robust royal family, its multigenerational strength displayed yearly on the balcony at Buckingham Palace, become an existential threat?

Charles is 75 years old. He is ill, and though we are told his prognosis is good, it’s unclear when he may resume a full schedule.

Queen Camilla does her part, but she lacks star power.

Princess Anne is 73. Her esteemed work ethic notwithstanding, she doesn’t draw global media attention. She’s not a subject of fascination. She is the workhorse of the Windsors, and one wonders how long she can keep it up.

Where does this leave the royals? The future of a monarchy dimmed by the loss of Queen Elizabeth and further diminished by the withdrawal, for the moment, of Kate?

Could the dissipation of the once robust royal family, its multigenerational strength displayed yearly on the balcony at Buckingham Palace, become an existential threat? (Pictured: Top Gun premiere, 2022).

What of Prince Edward and Sophie? He is rarely seen, and it seems Sophie — otherwise so prominent during funeral services for Queen Elizabeth, so close was she to the late monarch — has been told to stand down.

And so it is left to William and Kate, the lone A-listers among the royals, to ensure the survival of the monarchy.

And if we’re really honest about it, Kate is the most important figure: The most glittering and — despite her origins as a commoner — really the most royal of the royals.

William at the BAFTAs last week did his best. But his lonely photograph with Tom Cruise called to mind the 2022 Top Gun premiere, when Cruise offered his hand to help Kate, beaming in her strapless black-and-white gown, up the red carpet stairs while William, somewhat haplessly, looked on.

That moment said it all: Kate is the star, and everyone else — even Tom Cruise — is background.