On Saturday morning, tens of millions of people all over the world will switch on their screens to watch an elderly English couple borne in a rattling coach to Westminster Abbey, where they will be adorned with crowns much bigger than their nation’s modern importance justifies. The Royal Family are an element of Britain who still command fascination as a gilded soap opera.

A cynic may suggest that the absence from the ceremony of Meghan, Duchess of Sussex, will slightly diminish TV audiences. Had she attended, some people would have watched in order to see whether Prince Harry’s American wife would precipitate a row, or if one of the royals might gain revenge for all the grief her verbal assaults have inflicted on them.

As it is, King Charles III’s younger son — the “spare” as he calls himself in the title of his bestselling autobiography — will attend the ceremony but then hasten back to his new home in California, where he and Meghan seem more valued than they are in Britain. Before he flies, however, the worldwide audience will be treated to a spectacular such as the British do better than anyone else, with guardsmen and jingling cavalry, robes and jewels, pageantry and bands to stir the chilliest republican heart.

Even some of those British people who are a tad embarrassed by all the fuss about the crusty old Prince of Wales and his longtime lover being transformed into King Charles III and Queen Camilla may sneak a look. Amid the nation’s economic and political troubles, it is great to be offered a show that will cheer us up, even if we don’t purchase the tacky souvenirs.

After decades of harsh media dissection of the eccentric Charles and, especially, of his disastrous previous marriage to Princess Diana, there is today a groundswell of public eagerness for his reign to succeed. We want to be pleased with him. Unexpectedly, he seems to offer at least the possibility of following his mother as a bastion of stability in a nation that is suffering a protracted crisis of self-confidence.

Since Queen Elizabeth II’s death on September 8, the King has scarcely put a foot wrong. Beyond a flash of petulance of the kind that provoked much criticism in the past, when a pen with which he was attempting to sign a document ran dry, he has behaved with regal graciousness, and even smiles quite a lot. His state visit to Germany last month was rated a triumph.

Some of the credit for this belongs, well past most adults’ retirement age, to him getting the top job for which he chafed so long in waiting. But much also seems to have been achieved by his wife, who jollies him along and travels the country displaying a good humour and charm that has won over many past doubters, including me.

In times gone by, Camilla Parker Bowles’s role as the King’s almost lifelong lover — the “third person” in his last marriage, as Diana bitterly described her in a notorious 1995 BBC TV interview — seemed somewhat sordid. As a newspaper editor, in that year I chanced to be having lunch with the Queen’s private secretary. I mentioned to him that I had heard that the Parker Bowleses, already separated, were finally getting divorced.

My guest dropped his knife in shock and dismay. Despite his key role at Buckingham Palace, no one had bothered to tell the Queen’s most senior bureaucrat about this development. So distant were relations between Elizabeth and her son that I do not believe the monarch knew, either. My friend the private secretary considered the news entirely unwelcome. It created the possibility of Charles eventually marrying Camilla, which he believed to be a disastrous prospect: “If he marries her, she will become Queen. And I don’t think the British people will like it!”

Almost 30 years ago, I agreed with that view. Today, however, most of the King’s subjects have forgotten the details of Charles and Camilla’s long, closeted relationship, if they ever knew them. In an age when divorces, and indeed royal divorces, are commonplace, they are willing to forgive and forget. They are merely content that Camilla, as the King’s wife, seems to have provided a happiness that eluded him for most of his life, even if some of us are a bit queasy that he has insisted upon his once-adventurous wife being given her own crown.

It is a reflection of the extraordinarily small galaxy of British royal masters, mates and mistresses that among the guests in the Abbey on Saturday will be Andrew Parker Bowles, once Camilla’s husband, father of her two children — and still her closest confidant. It is almost satirical that this dashing figure, always addressed by friends as “Brigadier”, in his younger days romanced Charles’s sister, the Princess Royal, among many others — and commanded the cavalry escort at Charles’s 1981 wedding to Diana.

To call the Brigadier a charmer is faint praise. Some years ago, my wife and I entertained him to dinner and sat him next to a beautiful young Canadian woman whom he had never met before. When she left, she appeared dazed by the experience of being teasingly interrogated by the infinitely mischievous ex-soldier: “I told him things I have never told anybody, about my first lovers!” The key to Andrew and Camilla is that both are fun. This King will never be fun, but his remarriage seems to have made him less gloomy and self-pitying.

The transition from Queen Elizabeth to King Charles has been accomplished with none of the national trauma that was widely predicted during the former’s lifetime. Since Charles’s accession to the throne, the couple’s public relations have been skilfully managed. Camilla used to be considered lazy. Today, although visibly stressed — who would not be, as a commoner now trapped in a gilded cage? — she displays a chummy lack of pretension that wins applause. At 75, she can scarcely match the glamour of the dead Princess Diana. But the notoriously vicious British tabloid press have allowed the new monarch and his consort an unexpected honeymoon from criticism.

In the eyes of us monarchists, all this is welcome. There is no rational case for having a hereditary head of state, drawn from a family who have as much German as British in their ancestry. Yet wherever we look around the world at elected presidents, we thank our stars for denying such people the role of head of state in our own polity.

I doubt, however, whether Charles will continue to receive such an easy ride, enjoy a continued media holiday, much past Saturday’s ceremony. For a start, he is old. This makes it inevitable that his reign will lack the stardust that fell upon the young Queen Elizabeth when she ascended the throne in 1953 — and that would have been sprinkled on Prince William and his wife, Kate, had Charles chosen to retire to commune with the trees at his beloved private home, Highgrove, leaving his elder son to take the crown in his place.

In the natural order of things, it now appears that William will be middle-aged by the time he becomes the King. True, there is no precedent for the job skipping a generation in favour of young blood, but I am among those who thought that for Charles to pass the parcel, or rather the orb and sceptre, would have been a smart call.

The biggest threat to Britain’s monarchy comes not from its active opponents, of whom there are still relatively few, but instead from the much larger proportion of the population, especially the young, who are indifferent. My wife and I, as children, avidly watched Queen Elizabeth’s coronation on television, as did most of the country. Our Berkshire village, like thousands of other communities, held a celebratory fete attended by almost every inhabitant, at which I ran a darts stall.

There is little of that sort of thing scheduled for the coming weekend. My children and grandchildren doubt that they will bother to watch the ceremony. They are not republicans, just not interested. I believe they would be more engaged if William and Kate were occupying the coronation coach, rather than the old folks.

A YouGov poll last week showed that while 58 per cent of British people continue to support the monarchy, 26 per cent favour having an elected head of a state. And while 78 per cent of over-65s support keeping the King, only 32 per cent of those 18 to 24 feel the same way. Some 38 per cent of this young group want an elected head of state, and I doubt that they will become more monarchist as they get older.

Next, I think Charles’s personal oddity — and he is indeed odd — will resurface, creating embarrassments. He carries with him to every house in which he stays his own towels and suchlike — even organic wine. If any of the rest of us did that sort of thing, we would be accused of intolerably self-indulgent discourtesy.

Next up, many of us expected that once Charles assumed the throne, some of the absurdly extravagant portfolio of palaces and houses — Buckingham Palace, Windsor Castle, Balmoral, Sandringham, Clarence House, Highgrove, Dumfries House and the Castle of Mey, to name only the most prominent — would be disposed of. As it is, Charles recently commissioned a new topiary garden at Sandringham, which will cost hundreds of thousands of dollars.

There is scant sign of economies in his property holdings or anything else. A courtier once described him to me as “the most innumerate man I know”, meaning that he has no sense of what anything costs, because no one has ever made him think about this, although his mother thought about it constantly. The secrecy surrounding the transfer of the Royal Family’s vast wealth to the new generation, free of all taxation, has also left a bad taste.

Charles possesses a truly regal sense of self-entitlement, familiar in the 18th century but pretty potty in the 21st. Few of the British people want a bargain-basement “bicycling monarchy” on the lines of the Scandinavian or Dutch ones. At a time of severe national economic hardship, however, it seems rash for the King to sustain his accustomed profligacy.

He deserves, and nowadays receives, full credit for his pioneering commitment to highlighting climate change through four decades. But his general approach to the environment is rooted in unrealism, because he is oblivious of economics. For years, he urged switching swaths of British agricultural land from arable to grassland. He seemed not to notice that it would be impossible to find animals to profitably graze this. He is also widely criticised as a hypocrite for constant use of private jets and helicopters, heedless of his own carbon footprint.

The King’s good intentions are not in doubt, but his intellect is undisciplined because no one has ever insisted that it should be anything else. A friend of mine who was at the helm of a government anti-drugs commission was one day invited to Highgrove to discuss her work. She afterwards described to me, with some exasperation, how Prince Charles permitted her to talk for ten minutes about drugs, then suddenly interjected: “Isn’t it appalling what is happening to the Brazilian rainforest?”

I remain optimistic for Britain’s monarchy if the King preserves the discreet silence about public issues he has adopted since his accession; if Camilla continues to play her unexpected role as a national auntie; and if he imposes tough cuts on the overextended and pretty unlovable Royal Family and their embarrassment of palaces and expectations.

Saturday’s coronation circus will almost certainly be a success because the British are good at these things. I feel a pang of sympathy for Harry, who will assuredly brood throughout the ceremony that it should have been his own mother who receives a crown, not the Camilla whom he despises. But that is showbusiness.

Of course, in the 21st century, royalty is all nonsense, but it is relatively harmless nonsense that gives pleasure to many people. The royal brand is a real marketing asset for Britain — something the French and Germans do not have and, dare I say it, of which many Americans are sort of jealous. “Long Live the King!” sounds a weird slogan when the old boy is 74. I am more inclined to cry, “Long live the monarchy!” to prevent the ilk of Boris Johnson or Donald Trump from becoming our head of state, heaven help us.

• Max Hastings is a Bloomberg Opinion columnist. A former editor-in-chief of the Daily Telegraph and the London Evening Standard, he is author, most recently, of The Abyss: Nuclear Crisis Cuba 1962