Kate Middleton attended a final rehearsal at Westminster Abbey on the eve of her wedding as Prince William delighted crowds of wellwishers with an impromptu appearance.
The casually dressed prince was given a welcome worthy of a rock star as he appeared on The Mall, the wide boulevard leading to Buckingham Palace where hundreds of people were preparing to camp out overnight.
Earlier, the couple said they had been "incredibly moved" by the affection shown to them since they announced their engagement in November.
In a message in their official wedding programme, William and Kate thanked "everyone most sincerely for their kindness" as they prepare for "one of the happiest days of our lives".
The Order of Service revealed that Kate will not promise to obey her husband in her marriage vows, following in the footsteps of William's late mother Diana, who later divorced his father Prince Charles and died in a Paris car crash in 1997.
In Friday's ceremony, 29-year-old Kate will pledge to "love, comfort, honour and keep" William rather than the more traditional vow to "obey" him.
With 24 hours to go to the wedding, weather forecasters had good news for the 600,000 people expected to gather to watch the ceremony, predicting a cloudy but dry start to Friday, with only a small risk of rain.
In a diplomatic row that threatened to overshadow the good mood, Britain abruptly withdrew the Syrian ambassador's invitation to the wedding, saying the regime's crackdown on protesters made it unacceptable for him to attend.
The invitation had attracted controversy following claims from rights groups that more than 450 pro-democracy protesters have been killed in Syria by security forces in recent weeks.
"Buckingham Palace shares the view of the Foreign Office that it is not considered appropriate for the Syrian ambassador to attend the wedding," a Foreign Office statement said.
The Syrian envoy, Sami Khiyami, said the decision was "embarrassing" and blamed the media for forcing the British government's hand.
"I find it a bit embarrassing but I don't consider it as a matter that would jeopardise any ongoing relations and discussions with the British government," he told BBC Radio.
"I don't really understand it but I understand the influence of media on the government decisions."
Visiting well-wishers on the wedding route on Thursday evening, Prime Minister David Cameron said: "The right decision was taken."
Preparations for the biggest royal wedding in Britain for 30 years reached fever pitch as Kate attended a second and final rehearsal at Westminster Abbey early Thursday, accompanied by William's brother and best man Prince Harry.
She later made a brief appearance outside The Goring hotel, where she will spend her last night as a single woman, delighting the crowds with a wave.
A canopy has been erected over the front of the hotel to ensure no one sees her wedding gown until she arrives at the abbey on Friday.
On The Mall, which the newlyweds will travel down in a horse-drawn carriage, hundreds of people were preparing to spend a chilly night to get a good view of the procession.
Ruth Jackson, a head teacher from Wales, said: "It's history in the making. We've never been to a royal event before so we wanted to come and soak up the atmosphere. It hasn't disappointed us."
Cameron praised the "fantastic atmosphere" as he walked through the crowd, and Prince Charles' wife Camilla also joined the throng, saying: "We're all ready for tomorrow -- it's wonderful and all very exciting!".
Camilla and Charles attended a reception along with the queen on Thursday night being given for British and foreign royals attending the wedding at the Mandarin Oriental hotel in central London.
As final security checks were carried out, meanwhile, police said they had arrested 20 people across London after warning they would act to prevent anyone causing trouble during the wedding.
