Royal wedding day dawns in London

Enthusiastic crowds await the Royal Wedding in Parliament Square, London, April, 29, 2011.
Updated at 5:17 a.m. Eastern

LONDON (AP) - From Buckingham Palace to Westminster Abbey, royal fans lined the streets of London by the tens of thousands Friday, hoping to snatch a glimpse of history as Prince William weds Kate Middleton in a marriage expected to revive Britain's beleaguered monarchy.

About 45 minutes before the ceremony was due to begin, Prince William and his brother and best man Prince Harry left their official residence at Clarence House for London's storied Westminster Abbey. They drove down The Mall - a broad avenue through central London - and waved at thousands of adoring fans lining the route.

The royal family announced three hours before the main event that Prince William and Kate would gain the titles of Duke and Duchess of Cambridge following their nuptials.

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Royal wedding in Pictures

A third of the planet was to watch as the future king and queen of England start their lives as husband and wife with the two simple words "I will," ending months of buildup and sealing their love with the most public of spectacles.

CBS News' live coverage of the royal wedding

Celebrities, sports stars and royalty flocked to Westminster Abbey before the royal wedding.

Among the hundreds of guests filing into Westminster Abbey were soccer star David Beckham and his Spice Girl wife Victoria. Chelsy Davy, Prince Harry's on-again-off-again girlfriend, was already seated.

The Great North Door opened Friday morning under three hours before the ceremony was due to begin.

All the clamoring over every detail - the wedding dress, her hair, her makeup, the romantic kiss on the Buckingham Palace balcony, the honeymoon - finally will be answered.

Save perhaps for the biggest question of all: Is this one royal couple who will live happily ever after?

Will their union endure like that of Queen Elizabeth II and Prince Philip, now in its 64th year, or crumble spectacularly like that of Prince Charles and Lady Diana Spencer, William's own parents?

Recent history augurs badly: The first marriages of three of the queen's four children ended in divorce. But the couple's chemistry brings confidence that this one will work.

William and Kate look fantastic together, seeming to glow with happiness in each other's company, and unlike Charles and Diana they've had eight years to figure out they're made for each other.

But the fate of their marriage will depend on private matters impossible for the public to gauge amid the hoopla. A beautiful bridal gown and eye-popping sapphire and diamond engagement ring do not guarantee a happy ending. Money, power, beauty - it can all go wrong if not carefully nurtured.

Much will depend on whether 28-year-old William and 29-year-old Kate can summon the things every couple needs to make a marriage work: patience, love, wit and wisdom. But they face pressures most of the world doesn't: the twin burdens of fame and scrutiny.

These are the thorny issues upon which the fate of the monarchy rests, as the remarkable Queen Elizabeth II, now 85, inevitably ages and declines.

With just hours to go, dedicated royal watchers camped outside got an unexpected surprise - a visit from Prince William.

The groom-to-be emerged from his residence Thursday night to greet the hordes of well-wishers gathered along the processional route. Dressed in khakis and grinning broadly, William shook countless hands as his photo was snapped on cell phones and digital cameras.

By dawn on Friday, crowds were awake and waving flags for television cameras under steely gray skies. Technicians ran last-minute checks on huge television screens that will broadcast the ceremony at Trafalgar Square.

Despite the forecast of scattered showers, William and Kate Middleton will brave the elements and travel from the abbey to Buckingham Palace in an open-topped carriage, royal officials said.