Roughly a decade ago, Britain's best hope of a republic came and went in the space of 48 hours. Personally, I blame Elton John, the potency of cheap music, London's florists and Charles Spencer. Tony Parsons, standing stricken behind me in the media queue for the abbey, probably didn't help. I almost offered him a hankie. He takes his patriotism seriously, that one.

My own hopes that this time, finally, the House of Windsor had pulled the roof down didn't amount to much. That institution has never depended greatly on our good opinions, despite all conventional wisdom. Being dim, greedy, scandalous, remote or anachronistic has rarely put a dent in the unthinking affection awarded to the royals. Where monarchy is concerned, Britain requires psychotherapy, not constitutional reform.

Besides, despite the family giving every impression that they were not too fussed over who had died, or why, in the Alma tunnel in Paris, Diana was a strange vessel for the carriage of republican beliefs. Apart from anything else, she shared not a single one of them. Money aside - if money can ever be put aside in discussions of the in-bred - her central concern during her divorce was her title. The heir could treat her with disdain and worse, but she was not about to give up being a princess for anyone.

You got a sense of that listening to her brother's famous eulogy. The mob outside - for a mob is what it was - decided he was speaking for them. You could hear their approval, their cheers and applause, like distant rainfall on the roof of the old church. But aside from settling a few old scores, Charles Spencer was making a different point, a point his sister is alleged to have made to the Duke of Edinburgh himself, once upon a time.

Phil, they say, threatened to have Diana stripped of her title. What a card. She, not quite as thick as the plank to which she once compared herself, replied that her Spencer lineage was a good deal more ancient than anything the consort could claim. That was her brother's real message to the Windsors, a cliché among the older aristos: you are upstarts, whatever the unwashed have been led to believe, and we outrank you. Not quite the attitude of the sans culottes, I think.

It explains, nevertheless, why Diana's death was never likely to "bring down the royals". A princess, even a deceased "people's princess", could not have become the avenging angel of our undeclared republic. Her cult - 10 years on, we are still writing about the woman - has nothing to do with egalitarian ideals, and everything to do with myths of rank, breeding and the enchantments of title. Yet having seen off Wallis Simpson, the commoners' commoner, the Windsors thought they knew how to manage Diana. She stripped aside a couple of their veils, nevertheless. In the 48 hours after her death the former in-laws revealed that the difference between royal dignity and callousness is slight indeed. They showed that their supposedly intimate understanding of the subject class barely exists. Above all, they demonstrated that the legendary guile and expertise of "the Firm" is a fiction. Tony Blair's excruciating performance aside, the aftermath of Diana's death was a PR disaster.

In London, at least, the anger was authentic. On the night before the funeral the vast encampment in Hyde Park seethed, held in check only by notions of respect and grief. It became fashionable, after the event, to talk in terms of mass hysteria, but pop psychology does not explain what was going on. People wept for a woman they had never met, but they wept sincerely. They were disgusted with individuals they knew only from photographs, but the disgust was raw and real.

That was the problem, I think, for anyone who hoped that something useful might emerge from a stupid accident. Everything became symbolic. It mattered more whether a respectful flag was lowered above Buck House than whether anyone stopped to wonder about the building or the emblem. If anything, in fact, the mass anger that followed Diana's death was an affirmation of royalty's place in the United Kingdom. We - though you can speak for yourself - didn't want shot of them; we just wanted them to get it right, to do the decent thing, to honour the fiction.

In that sense, Diana was always irrelevant. A decade on, the enduring mystery surrounding a young woman's passing has less to do with the phenomenon of mass grief than with an inability - a refusal - to draw conclusions. The princess would not have thanked you for a republic. Elton's tune, apt for Marilyn, not for the wannabe, was no call to citoyens. But faced with the evidence of the Windsors' emotional paralysis, intellectual incapacity and sheer brutishness, why did so few people say: hold on a minute?

Ten years ago, it was common coin to assert that royalty faced a crisis. Cynics among us - me, at any rate - were prepared to guess that the death of a very old lady might heal a few breaches, that two boys would be marketed relentlessly, and that the heir's paramour would be eased in the direction of public acceptance. The Windsors exist, after all, in order just to persist. They endure no matter what. It was one thing, in that circumstance, to predict engulfing crisis, quite another to say how it might unfold.

Or rather, to say how it might be allowed to unfold. An extraordinary number of things in British life depend upon the crown. Constitutional lawyers will tell you happily that the concept is an elegant fiction, albeit one that allows Westminster government to function, but an unwritten fiction nevertheless. They forget to add that for "the Crown-in-Parliament", and the rest, to work, you need a breathing monarch.

Then you need heirs and spares. You require approved breeding units who do not kick over the traces. You need ceremonial occasions, and ceremonial functions. A peerage will likely give the thing the appearance of durability. Signets and seals will be called for; chivalric fictions and redrafted histories will be unavoidable. If it appears useful to have boys die vainly in some stinking backwater for Queen and Country, first attach a queen to the relevant country. And allow no-one to sever the solemn bond.

Even if she had been so minded, Diana never possessed the firepower to put a crimp in that. The Windsors survived her because - no approval is implied - they serve a larger purpose. The dissident republican minority failed because it pinned hopes on a self-confessed airhead toff, rather than on a persuasive argument. The Windsors bounced back, as always. It is, in essence, what they do. They depend on a public with the collective attention span of the Household Cavalry. And they know that the British establishment needs them, truly needs them, to keep the show on the road.

William and Harry - so like their mother, and their fathers - will distract attention for another decade or three. The reform of democracy will be haggled over without a thought given to its symbolic and actual capstone. Subjects will go on being confused with citizens. And Elton will probably still be singing a song that isn't Bandiera Rossa.