Prince William and Kate Middleton say they have been “incredibly moved” by the affection shown to them since they announced their engagement, the BBC reports.
In a message in their official wedding programme they thanked “everyone most sincerely for their kindness”.
During Friday’s Westminster Abbey ceremony Miss Middleton will vow to “love, comfort, honour and keep” Prince William but will not vow to obey him.
The service will be the epitome of “Britishness”, St James’s Palace said.
VisitBritain has predicted more than 600,000 people will be on the streets to watch Friday’s events and several hundred are already camping out in tents and sleeping bags outside the abbey and in The Mall near Buckingham Palace.
The Duchess of Cornwall left her London home Clarence House and went on an impromptu walkabout to meet some of the fans in The Mall.
She described Prince William and Miss Middleton as being “all ready” for their big day and said the Royal Family were “very excited”.
Meanwhile, the Foreign Office says the invitation for the Syrian ambassador in London has been withdrawn following reports that up to 400 pro-democracy protesters have been killed in Syria by security forces in recent weeks.
A Foreign Office statement said: “Buckingham Palace shares the view of the Foreign Office that it is not considered appropriate for the Syrian ambassador to attend the wedding.”
Earlier on Thursday Miss Middleton took part in her last rehearsal at Westminster Abbey, with best man Prince Harry, the bridesmaids and pageboys.
Prince William is due to spend Thursday evening with the Prince of Wales, Duchess of Cornwall and Harry.
Miss Middleton and her family are gathering at the Goring Hotel, in Belgravia. She arrived at the hotel at about 1745 BST accompanied by her mother and stood outside for a short while as photographers took pictures.
Some 50 foreign heads of state are among the 1,900 invited guests attending the wedding.
The Queen is due to host an event for British and foreign royals at the Mandarin Oriental Hotel, near Hyde Park, in central London on Thursday night.
But it has emerged that she will leave for a weekend away after hosting the wedding day lunchtime reception, giving over Buckingham Palace for William and Kate’s black tie party in the evening.
It means the Queen and Duke of Edinburgh will miss Prince Harry’s best man’s speech and Michael Middleton’s father-of-the-bride address.
The souvenir wedding programme is available to download free as a PDF from the official Royal Wedding website. The booklet will be sold for £2 a copy along the processional route, with proceeds going to the Foundation of Prince William and Prince Harry.
Train companies have warned 400,000 people are expected to travel by train into central London on Friday – a 15% rise in passengers compared with a normal public holiday – but say they will be able to cope.
It is anticipated the events will be watched by millions of people worldwide on television. Thousands of journalists have descended on London and makeshift studios are outside Buckingham Palace and along the wedding route.
Scotland Yard has indicated it would take pre-emptive action to stop people causing trouble and said it “brought forward” three raids on premises in the capital, believed to be occupied by squatters, because of the wedding.
But Labour backbencher John McDonnell raised a point of order in the Commons describing the action – which the Metropolitan Police said was not “specifically related” to the wedding – as “disproportionate”.
The Met Office says Friday will start off dry but cloudy in London. It will become brighter through the morning, with some sunny spells, but there is a 30% risk of showers about noon when Prince William and his bride are expected to emerge from Westminster Abbey after the wedding.
Forecasters also say there is a risk of heavy showers developing later on. Temperatures in the capital are expected to reach a high of 19C (66F) in the afternoon.
Many workers have taken holiday time off during this week, which has two public holidays – Monday and Friday. Migrant workers will be out in force during the wedding serving in the many bars, restaurants and hotels in London.