LONDON, April 28 (Reuters) - Crowds camped out in London and dignitaries flew in for Friday's wedding of Prince William and Kate Middleton, an event full of pageantry that has drawn Britain and its monarchy into the international spotlight.
Showing that behind the royal spectacle lay serious political sensitivities, Britain withdrew Syria's invitation, saying its crackdown on pro-democracy supporters made it inappropriate that its ambassador should attend.
Recalling William's mother, Princess Diana, who was killed in a car crash in Paris in 1997, the couple have chosen to lead the hymns at the marriage with the final hymn that was sung at her funeral in Westminster Abbey where the couple will marry.
In a message of thanks to well-wishers worldwide, the couple said they were deeply touched by the outpouring of affection ahead of a wedding service that will combine ancient traditions of the monarchy with a sense of modernity to reflect the times.
In the service, Middleton will not promise to "obey" William as part of her wedding vows in front of royals, politicians, celebrities, family and friends.
Amid final preparations, Middleton, 29, attended a rehearsal on Thursday at the abbey, the coronation church for the monarchy since William the Conqueror in 1066, accompanied by William's younger brother and best man Prince Harry.
"We are both so delighted that you are able to join us in celebrating what we hope will be one of the happiest days of our lives," William, the second in line to the throne, and Kate wrote in a statement printed in an official souvenir programme.
DIANA CONSPICUOUS BY ABSENCE
Diana's friend Elton John, who sang "Candle in the Wind" at her funeral, will be a guest on Friday and William has given Kate his mother's dazzling sapphire and diamond engagement ring.
The royals' cool reaction to Diana's death contrasted with an outpouring of public grief and marked a low point for the monarchy. Some questioned whether the institution, a vestige of imperial glory, had outlived its unifying role in a modern state divided by partisan politics and regional separatisms.
William's marriage to Middleton, who is from an affluent middle-class background and a commoner rather than an aristocrat, is seen as adding a renewed dash of glamour to a faded brand and more in step with contemporary Britain.
On the street across from the abbey, crowds began to swell at a makeshift campsite, with tents draped in British "Union Jack" flags, pictures of the couple and banners reading "It's cold but worth it" and "It could have been me".
"I'm a romance novelist so I had to come for the most romantic event in the world," said Sheree Zielke, 55, who has travelled from Canada to watch the event which has been met by republicans with indifference and by royalists with excitement.
Tourism chiefs are predicting an extra 600,000 visitors in the capital on Friday, taking the total to about 1.1 million and bringing in up to 50 million pounds ($80 million).
Security will be tight on the day, with Britain on its second highest threat level meaning an attack by militants is considered "highly likely", and police have been carrying out thorough searches along the route.
Militant Islamists and Irish republicans, anarchists, and stalkers are all seen by security experts as possible risks.
"UNION JACKS" AND PARTIES
Across London, flags and red, white and blue bunting fluttered across buildings and shops, with similar scenes in cities, towns and villages across the country.
Prime Minister David Cameron said Britons "felt deeply" about their constitutional monarchy, which went through scandals in the 1990s notably the divorce between William's parents, Prince Charles and Princess Diana.
"This is like the team of the future," he told Sky News.
Some Britons, however, are far from excited, either indifferent or positively hostile as the wedding comes at a time when the government is pushing ahead with austerity measures involving deep spending cuts and large-scale job losses.
While the royal family and the Middletons will pay for the ceremony and reception, the taxpayers will foot the bill for security costs, which republicans say could exceed 10 million pounds.
An Ipsos MORI poll for Reuters this month found 47 percent of Britons were either not very, or not at all interested.
"I want to get as far away as possible from the wedding because it really doesn't mean anything to me, so my wife and I are going for a long weekend to Italy," Londoner Alex Joseph told Reuters.
Artist Ollie Sam, 26, commented: "It makes me laugh that many people here are leaving town to get away for the long weekend, while foreigners are coming to see the wedding. I personally think it's a waste of money."
The government estimates about two million people would take part in some 5,500 street parties in England and Wales, although officials said it appeared from requests for celebrations that the affluent south was more royalist than the poorer north.
Economists also estimate the extra public holiday will cost billions of pounds and could damage Britain's fragile economic recovery, with one saying it will knock a quarter of a percentage point off second-quarter GDP growth.
WORLD HUNGERS FOR ROYALS
Outside Britain, the world's fascination with the British royal family is undiminished. An estimated 8,000 journalists are in London to cover the ceremony, and hundreds of millions across the world will watch on television.
That interest partly stems from the lasting appeal of William's mother Diana, particularly in the United States.
William, now 28, was 15 when his hugely popular mother was killed and the image of the prince and his brother Harry walking behind their mother's funeral cortege was striking.
While Diana's death marked a low point for senior royals, supporters hope William's wedding will ignite enthusiasm and modernise the monarchy's stuffy, outdated image.
He faces a long wait for the throne, however -- his grandmother Queen Elizabeth shows little sign of slowing down at 85 and his father Charles is a fit and active 62-year-old.
Diana's divorce, death and other scandals saw support for the House of Windsor dive in the 1990s but their ratings are now much improved. Three quarters of those polled for Reuters last week said they favoured Britain remaining a monarchy.
Middleton, whose mother's family is descended from miners, will be the first commoner to marry a monarch-to-be since Anne Hyde wed the future James II in the 17th century.
Commentators say this is bound to help the royals' image of being able to adapt and modernise.
"Their marriage will breathe new life into the monarchy as the queen enters the twilight of her reign, bringing new blood and a fresh perspective to an institution that faces criticism for being elitist and out of touch," royal biographer Claudia Joseph told Reuters.
(Additional reporting by Avril Ormsby, Mike Collett-White, Christina Fincher and Marie-Louise Gumuchian; editing by Paul Casciato and Peter Millership)
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