If Charles really wants to marry Camilla, he should

But we should give very little weight to Mr Burrell’s claim that Diana believed she would be murdered, or that the circumstances of her death demand fresh examination. This cause - taken up by publications as varied as the Mirror and Tatler - merely feeds the conspiracy theorists while doing no good to the living.

Paranoid people - and the late princess undoubtedly became one - generally believe that someone is trying to kill them. In fairness, the stricken princess did have an unyielding family ranged against her when her marriage to Charles began to founder. It is not altogether surprising if she succumbed to the belief that they were out to get her. That does not make it true.

The instant wisdom is that this will "set back" the cause of Camilla and her hopes of marrying the prince. I very much hope not.

I happened to pass Camilla Parker Bowles at the airport a couple of weeks ago. She was travelling with a friend and carrying her own luggage, clipping determinedly through Terminal One with her partridge-like gait. You could not mistake her for anything other than a jolly, down-to-earth, upper-class woman, secure enough in her identity to stick to her Seventies hair flicks.

That is Mrs Parker Bowles’s low-key appeal. Even when she glammed up for the Fashion Rocks last week, her teasing conversation with a top designer was about what it would take to give her a rock-chick look. An improbable thought.

The idea that the public would "never permit" Charles and Camilla to marry always strikes me as inane. The public - and that means all of us - is not in a position to dictate terms to the Royal Family about their marriages, and neither should it be. Public opinion has warmed to Camilla - not with the same ardent flare as Diana provoked, of course, but we could tolerate her perfectly well. It does rather seem as if the Queen and Duke of Edinburgh are the real impediments to a marriage. That is ill-advised, though not for want of advisers - there seem to be a whole army of them.

The longer uncertainty remains over the relationship of Camilla and Charles, the more uncertain the monarchy appears. If they cannot establish their right to marry, how on earth can they contend with the other more substantial problems of how a modern royalty should function?

An enlightening new book by the journalist Rebecca Tyrrel, Camilla: An Intimate Portrait, tells us that here are a couple who have been in love for the best part of 30 years and who want to remain together. Very well. But given Charles’s role as heir to the throne, it does not seem quite enough to conclude that they should just rollick on their merry way.

The most compelling part of Mr Burrell’s book is the evidence within the letters showing just how much Camilla was seen in the Royal Household as a threat. "I can’t imagine anyone in their right mind leaving you for Camilla," said Prince Philip. Well, I can’t imagine anyone in their right mind saying that it makes sense for anyone to oppose the union of a couple who have had their other marriages, children, tragedies and regrets but ended up back together despite everything.

If Charles genuinely wants to marry Camilla, he should, even if his parents disapprove. One of the most important social functions of marriage is to settle and soothe turbulent pasts in a way that living together cannot.

As long as they remain unmarried, each time there is some new revelation about Diana, the ire will turn on Camilla and her part in Diana’s suffering. That would abate if there was a formal new union.

Why does it matter? Because the Royal Family is part of the continuum of British life and as such, part of all our stories. Republicans tend to underestimate the fact that people like having it around. The alternatives show no sign of appealing to us. In this post-devolution age, the monarchy is also the institution best placed to summarise the wholeness of the United Kingdom: a task its senior members should take more seriously by devoting more time to Scotland, Wales and Northern Ireland than the odd fleeting visit and shooting party allow.

The Prince of Wales has put impressive energy into his various causes. He has social commitment. He can be foolish in some of his concerns and the way he expresses them: but that is better than being a distant and uncaring heir.

My own preference is that the Crown should be handed on before the death of a reigning monarch - not in the spirit of abdication, but as a royal retirement to be celebrated. It is a more humane way of transferring the Crown between generations than waiting for sturdy old people to die off, while the young grow frustrated awaiting their turn.

But all these debates presume that the current unresolved situation of the Prince of Wales and Mrs Parker Bowles is clarified. What is so wrong with Camilla? Why should her status be subject to the backwash of every fresh Diana revelation? Why should she live her life as hostage to a ghost?

She is a steadying influence on the prince. Her only drawbacks are those of her class - an ingrained selfishness and an uncomplicated philistinism. Ms Tyrrel reveals Camilla responding to Charles’s cultural aspirations by saying at a Highgrove dinner: "This isn’t going to be one of those bloody musical evenings is it?" We don’t know whether to tut or giggle. I think we could get to like her.

At the end of The Madness of George III, the valet admonishes the servants who have witnessed the king’s deliriums: "Forget what you have seen here: Majesty in its small clothes." Now we get the majesty without any clothes and know more details about the royals’ private lives than we do about our own families.

And yet, the Royal Family has staying power and meaning for so many people, and it will do so for a long time to come.

If Prince Charles is a serious man, let him behave seriously and marry his Camilla. The House of Windsor would be the stronger for it, his strength of character would not be more solidly proven - and Diana’s ghost might rest a little more quietly, too.