She woke up this morning a middle-class commoner from a Berkshire village, but by midday Kate Middleton will have completed her storybook transformation into a woman who will one day be queen.
The moment for which she has been preparing almost all her adult life will arrive when she makes her three-minute walk down the aisle of Westminster Abbey watched by two billion people worldwide.
Up to a million people are expected to line the streets of London for the most anticipated royal event in 30 years, on what the bride and groom described yesterday as "one of the happiest days of our lives".
Many of the best-kept secrets of the ceremony were finally disclosed yesterday when St James's Palace published the order of service online so that millions of people can join in at home. Ms Middleton will vow to "love, comfort, honour and keep" the prince, but will not "obey" him, following a precedent set by Princess Diana.
Prince William sprang a surprise by choosing to wear the distinctive red tunic of the Irish Guards, of which he is colonel, rather than the dress uniform of the RAF, in which he is a serving officer.
Television viewers will have to wait until 10.51am for a first glimpse of what will, by the end of the day, be the most famous dress in the world. That is when Ms Middleton steps out of the Goring Hotel in Belgravia in her bridal gown.
There was a huge clue to the identity of the dressmaker yesterday, as Sarah Burton, of the fashion house Alexander McQueen, arrived at the hotel. Ms Burton tried to cover her face with a fur-lined hood, but was clearly identifiable.
Ms Middleton got her first taste of the atmosphere building up in the capital when she arrived at the Goring at 5.40pm. Accompanied by her mother Carole (56) and sister Pippa (27), she was greeted by huge cheers from a crowd which had waited all day.
Hundreds of people who were preparing to spend the night along the Mall received an unexpected visit from Princes William and Harry, who stepped out of Clarence House for a walkabout to thank them.
Ms Middleton visited Westminster Abbey for a final run-through for the young bridesmaids and page boys, but it was also a chance to make sure her journey up the aisle is perfectly in time with the music.
In a personal message, signed "William" and "Catherine" in today's order of service, the couple thanked the public for their "kindness".
"The affection shown to us by so many people during our engagement has been incredibly moving, and has touched us both deeply," they wrote.
Meanwhile, a black-and-white photo taken by Mario Testino, and which appears in the royal wedding programme, shows the couple wearing matching white shirts.
The celebrated fashion photographer was a favourite of the late Princess Diana's.
An otherwise flawless build-up was marred only by a diplomatic row as the Syrian ambassador to London was struck off the guest list following the regime's killing of up to 450 pro-democracy demonstrators in recent weeks.
The final royal secret to be released today will be the titles by which the couple will be known from now on. Prince William is expected to be granted a dukedom. (© Daily Telegraph, London)