Each step has been rehearsed, each flower meticulously arranged, the aisle of Westminster Abbey transformed into a flowering avenue of trees.
With just hours to go before his wedding to Catherine Middleton, dedicated royal-watchers camped outside got an unexpected surprise -- a visit from Prince William.
The 28-year-old 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.
The visit lent further excitement to the carnival atmosphere near the abbey, where hours earlier 29-year-old Kate had a final run-through with William's best man, Prince Harry.
A throng of curious tourists, dedicated monarchists, souvenir vendors, William-watchers and Harry-hunters have turned the Union Jack-bedecked streets into a scene of festive chaos.
"It's a once-in-a-lifetime thing. Not many kings-to-be are going to be married anytime soon," said Sarah White, 26, camped out with her sister, Liz. "Everyone's making friends and is in good spirits -- or at least will be until tomorrow."
The only clouds on the horizon: the threat of rain and the intrusion of politics, with the British government revoking an invitation to Syria's ambassador to condemn a deadly crackdown on protesters that has left hundreds dead.
Also, Scotland Yard said officers detained three individuals in South London on Thursday evening on suspicion of conspiracy to cause public nuisance and breach of the peace. The suspects -- two men, ages 68 and 45, and a 60-year-old woman -- remain in custody at a local police station, authorities said. The police declined to give further details.
Today's ceremony has been planned like a military operation. More than 1,500 soldiers, sailors and air crew will be on duty to line the couple's procession route between the abbey and Buckingham Palace, just under a mile away.
An additional 5,000 uniformed and undercover police will be on alert for threats from Irish dissident terrorists, Muslim extremists, anti-monarchists, royal obsessives and drunken hooligans.
The royal nuptials, scheduled to begin at 6 a.m. EDT, will offer pomp and circumstance on a grand scale, starting with a global guest list of 1,900 that includes kings and queens, sports stars, music royalty, the couple's university chums, Royal Air Force pilots and charity workers, as well as friends and family.
Westminster Abbey itself has been remade into a blooming forest, with six field maples and two hornbeams lining the aisle to the altar.
The British government also hopes the wedding will lift people's spirits during a period of tough austerity measures.
The Conservative-led government is cutting $135 billion in spending through 2015, slashing hundreds of thousands of government jobs and sharply increasing university tuition and fees.
After this morning's ceremony, the couple will travel by carriage to Buckingham Palace and emerge onto the balcony for a precisely timed kiss -- at 1:25 p.m. (8:25 a.m. EDT) -- followed by a ceremonial fly-past of military aircraft.
Then the partying starts. About 650 people are invited to a luncheon with the queen, and later that night 300 close friends and family will attend a black-tie evening bash.