This cock-up is embarrassing the whole nation

It is tempting to find a juicy conspiracy theory behind the Queen's announcement that she won't be going to her son's second marriage ceremony. "It's a poisonous legal stew," say the lawyers, salivating.

"The constitutional implications are severe," say the doom watchers happily.

"It's a snub," say the newspapers. "No, she is just respecting Charles's brilliant decision to make it a lowkey ceremony," say Clarence House.

"Pull the other one," say the rest of us.

But having run Diana's household throughout the War of the Waleses, I'm certain the culprit is much more likely to be cock-up than conspiracy.

Not that it makes the current mess any more palatable. We're talking about our national showroom here and whatever the Queen's real reasons, Charles and Camilla's wedding is becoming a national embarrassment.

Nor can they - or we - just blame the stuffy courtiers. This is what happens when selfindulgent royal lovebirds hijack the stately old bus of British constitutional monarchy and head off into uncharted territory: the wheels fall off.

Who's going to come to the rescue? In times of crisis, royal advisors look to Downing Street for help, as they should. But I doubt if the New Labour breakdown truck is in any hurry to get to the scene, especially if there are more little mishaps in store (and with six weeks to go, it's a brave mechanic who says there won't be).

How did it happen? Well perhaps the love bus didn't heed a signpost from history.

"Things were better managed in my day." So said Camilla's great-grandmother Alice Keppel about the last time a Prince of Wales married his mistress. That was the Abdication crisis of 1936 and granny Alice knew what she was talking about - she had been the chief mistress to Edward VII.

Although King Teddy took his pleasures seriously, he also took good care to treat his Queen - the saintly Alexandra - with the respect she deserved.

Charles found that bit of the mistress game too difficult, as Diana discovered to her cost. But Alice was right: keeping hold of your mistress and your reputation was just a matter of good management.

Fast forward to 2005 and good management still seems in short supply. Reputations aren't doing too well either. Regularising his "nonnegotiable"-relationship with Camilla was supposed to be the crowning achievement of Charles's post-Diana spin campaign.

The future could still be happyeverafter and HRH the Duchess of Cornwall at least sounds royal.

But after a promising start the wedding bus now looks like something rejected by Scrapheap Challenge. No wonder the Queen decided not to be taken for a ride.

If and when the heavy lifters get the thing back on the road, Her Majesty will be found waiting at the church - or at least St George's Chapel - ready to welcome the survivors with a touch of real royalty and a suitably modest reception.

That's worth a loyal cheer.