LONDON (Reuters) - Crowds camped out in London and foreign dignitaries flew in from around the world for Friday's wedding of Prince William and Kate Middleton, a service full of pomp and ceremony that has thrust the monarchy to center stage.
Underlying the diplomatic minefield of an event taking place in the full glare of the world's media, Britain withdrew Syria's invitation, saying Syria's crackdown on calls for democracy made it inappropriate that its ambassador should attend.
Middleton, 29, accompanied by William's younger brother and best man Prince Harry, attended a rehearsal on Thursday at the wedding venue, Westminster Abbey, the coronation church for the monarchy since William the Conqueror in 1066.
In the evening, Prince William reached into the crowds waiting on the Mall, the ceremonial avenue running from Buckingham Palace, shaking hands and telling delighted members of the public he was focusing on "remembering the lines" for the "big day," a live BBC broadcast showed.
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 a congregation gathering royals, politicians, celebrities and friends.
"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, second in line to the throne, and Kate wrote in a statement printed in an official souvenir program.
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 came from Canada to watch the event -- which is being met by republicans with indifference and by royalists with excitement.
Cindy Sagar, from Oxford in central England, said she had been one of about 600,000 who watched the 1981 wedding of William's father Prince Charles to Princess Diana. "It was electric, it was one of the best days of my life."
Tourism chiefs predict an extra 600,000 visitors will be 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, as Britain is on its second highest threat level meaning an attack by militants is considered "highly likely," and police have carried out thorough searches along the route.
Militant Islamists and Irish republicans, anarchists, and stalkers are all seen by security experts as possible threats.
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 the constitutional monarchy, which went through scandals in the 1990s -- notably William's parents' divorce -- and has described the nuptials as "unadulterated good news."
Some Britons, however, are indifferent or hostile as the wedding comes at a time when government austerity measures are leading to 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 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 will join 5,500 street parties in England and Wales, though officials said the affluent south seemed more royalist than the poorer north.
Economists say the extra public holiday will cost billions of pounds and could damage Britain's fragile economic recovery, one saying it will knock a quarter of a percentage point off second-quarter GDP growth.
Abroad, the world's fascination with the British royal family is undiminished. An estimated 8,000 journalists have arrived in London to cover the ceremony, and hundreds of millions across the world will watch on television.
That interest stems partly from the lasting appeal of William's mother Diana, particularly in the United States.
Fourteen years ago, the world's gaze was upon William and Westminster Abbey for Diana's funeral after her death in a Paris car crash, and William and Kate want her to be remembered on Friday.
They have included the final hymn sung at her funeral among their choices; Diana's friend Elton John, who sang "Candle in the Wind" at her funeral, will be a wedding guest; and William gave Kate her dazzling sapphire and diamond engagement ring.
William, now 28, was 15 when his hugely popular mother died 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 -- their cool reaction in sharp contrast to a huge outpouring of public grief -- they hope William's wedding will ignite enthusiasm and modernize the monarchy's image.
Kate, from an affluent middle-class background, is seen as adding a dash of glamour, reportedly winning William's attention by appearing at a charity fashion show in little more than her underwear.
Diana's death and other scandals saw support for the House of Windsor dive in the 1990s but their approval ratings are now much improved. Three-quarters of those polled for Reuters last week said they favored Britain remaining a monarchy.
The revival of the family fortunes meant there was little opposition when Charles married his long-term lover Camilla in 2005, a marriage thought inconceivable less than a decade earlier because of Diana's public standing.
Kate, whose parents run a successful business and whose mother's ancestors were miners, will be the first commoner to marry a monarch-to-be since Anne Hyde wed the future James II in the 17th century.
"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, Marie-Louise Gumuchian and Michel Rose; editing by Peter Millership