Although he had to resort to extreme methods a couple of times, if Henry VIII did nothing else in getting through six wives, he assured himself pretty good billing in the history of England.

If children know just one thing about the country's kings and queens, it's probably his marital appetite, nowadays only found in the world of showbiz.

But in Tudor times Royal Weddings were not trivial matters. And neither are they in this century - the abdication of Edward VIII when he wanted to marry the American Mrs Simpson became the low point in the Windsor family's troubled dealings with marriage.

The Tower of London, where Anne Boleyn among others met their end

After the turmoil of the last ten years, Edward and Sophie's wedding will be no trivial matter either.

The Royal Family undoubtedly benefited in public relations terms from Prince Charles' and Prince Andrew's weddings. Worldwide attention, a sparkling show of pageantry, general goodwill towards the happy couple. But they were hardly the first times weddings had served other purposes.

At least part of Henry VIII's behaviour was because of his desire for an heir - the cold political facts of royal marriages were essentially about preserving the dynasty, stitching strategic alliances together, uniting or bolstering houses.

Which did not leave much room for love's young dream.

And even now, the considerations over choosing a suitable partner for a royal are rather more complicated than for ordinary folk.

Edward and Mrs Simpson: crisis for monarchy

First of all, is the prospective spouse a royal? If not, are they sufficiently aristocratic to have the benefit of any doubt? If not aristocratic, are they charming and graceful enough to carry it off regardless? And - whichever category they fall into - will they cut it?

Harold Brookes-Baker, publisher of Burke's Peerage, said it was very clear looking at the marriages in continental royal families that the political considerations had been sidelined for the more conventional criteria.

The British royals had made something of a similar move starting, he said, with the marriage of George VI to the current Queen Mother.

"Though she was from a very noble family, she was not from a royal family," he said. "I would say that that's the beginning of a dramatic change towards a more understandable monarchy."

The Queen Mother and Prince Andrew on her 97th birthday

Queen Victoria (who of course married the very royal Prince Albert, her cousin) was widely thought to have decreed that her family should not be restricted to royal spouses.

But Mr Brookes-Baker said he thought she had been misunderstood, and that she had meant that her relatives should be able to marry people like the Battenburgs whose royal status had been downgraded.

"She would not have envisaged the kind of marriage Prince Edward has in mind," he said.

The current Queen addressed the issue by following Victoria's lead, marrying a cousin, who was also an heir to the Greek and Danish thrones. Prince Philip took his mother's family name, Mountbatten - his father's family name was Schleswig-Holstein-Sonderburg-Gl�cksburg.

Prince Charles reached a compromise marrying Lady Diana, because although she was not royal she did come from a noble family.

"Very much like the Queen Mother, it was a very good compromise from a lineage point of view," said Mr Brookes-Baker.

But the approach taken by the European monarchies is an alternative.

"The present king of Norway lived with his present wife for a good number of years," he added. "His father was very concerned that it would be the end of the monarchy if his son married a commoner.

Prince Andrew marries Sarah Ferguson in 1986

"He married her and all was well except that she is one of the most disliked women in the country, and is blamed for the economic confusion over what the monarchy does and doesn't have.

"On the other hand, the king of Sweden was almost ready to vacate the throne, but he fell in love with a German interpreter from a solid middle class family. And I don't think anyone would disagree that she has saved the monarchy there."

Look before you leap

Marrying for anything other than love is, by most westerners' estimation nowadays, a bad move. But marrying into the royals without a good ponder over the impact on the rest of one's life (official functions, paparazzi etc etc) would be equally foolhardy.

"The post of a working royal is very different from other posts," said Mr Brookes-Baker. "The Duchess of York clearly did not understand the drill, and was not up to the duties. The Princess of Wales, for all her qualities, simply could not learn the drill, and that was not good."

It's all a complicated business, and probably nothing is further from the minds of the happy couple than the cold political implications.

But for a moment consider it - and particularly Sophie's former employment - in unromantic, dispassionate terms.

What wiser move could there be than a strategic alliance between the monarchy and the world of public relations?