The road to the engagement may have been protracted and stressful, but now comes the really hard part: finding the dress.
Every girl regards her bridal gown as the dress of her dreams. But this is not just any girl, nor is it just any wedding dress. A future Queen of England needs to factor-in massive considerations.
For a start, this will be the royal wedding of the cyber-century. When Lady Diana Spencer married in St Paul's Cathedral in 1981, 750 million people watched on television, while radio listeners upped the total audience to more than one billion. But that was in the days before the internet, when mobile phones weighed as much as a breeze block.
Kate Middleton's bridal gown is a dress that will go down in history. It will turn its designer into a global household name; it will set trends; and it will be seen by billions - and preferably not on Twitter or Facebook before she walks down the aisle.
But to whom will the 21st-century's "people's princess" entrust this most monumental of royal commissions?
First, it seems safe to assume she will fly the flag and choose a British designer. Second, Kate is very much her own woman and, given her strong-minded individuality, is unlikely to pick someone with royal "form", such as, for example, Samantha Shaw, who designed the bridal gowns for both the Countess of Wessex and Viscountess Linley, or Sassi Holford, who created the dress for Autumn Kelly's wedding to the Princess Royal's son, Peter Phillips.
Third, Kate has never been one for obvious fashion choices. Her wardrobe, assured and appropriate as it may be, is selected from reliable brands such as Jigsaw, Kew, LK Bennett, Katherine Hooker and Issa. So it has generally been safe rather than über-stylish - save for her two catwalk outfits: her appearance in lingerie at St Andrews in 2002, which was the moment that Kate first caught Prince William's eye and the fluorescent roller-disco get-up that she wore in 2008 - so her choice of designer probably won't be predictable.
Wedding watchers support a classic, safe pair of hands, such as Stewart Parvin, who has a royal warrant, or Phillipa Lepley, who dresses top-tier Sloaney brides, or Amanda Wakeley, who specialises in grand glamour.
Miranda Eason, editor of Cosmopolitan Bride and You & Your Wedding , said: "Stewart Parvin is classic with a hint of Hollywood, Phillipa Lepley is classic but a bit girlie, and Jenny Packham dresses the Hollywood royals, so she could also be a possibility."
Deborah Joseph, editor of Brides , suggests Kate might opt "for one of Diana's favourite designers such as Bruce Oldfield or Amanda Wakeley, "out of respect for William".
Another strong tip is the Brazilian designer, Daniella "Issa" Helayel, who set up her label in London in 2001, and who has been designing dresses for the bride-to-be for the past five years. It was a one-of-a-kind Issa dress and jacket that Kate wore when she and Prince William attended the wedding of his friend, Harry Meade, a few weeks ago.
Helayel, who is something of a muse for Kate, has been building up a bridalwear business alongside the signature printed wrap dresses which first brought her fame at London Fashion Week. Her most recent aisle outing was at the wedding of Jessica Simon, one of the daughters of the multi-millionaire Monsoon and Accessorize founder, Peter Simon. Helayel's clientele includes Keira Knightley, Madonna, Jennifer Lopez and the Princesses Beatrice and Eugenie, who are often front-row guests at her London Fashion Week shows. "I can't comment," said an Issa spokesman when asked if they will get the royal commission. "Nothing has been decided."
Kate could defy convention by choosing a gown by one of England's more outrageous couturiers. Dame Vivienne Westwood, for example, has made a fortune from her very regal corset-and-crinoline creations worthy of another Catherine, Catherine of Braganza, the wife of King Charles II - and also fit for queen of the small screen Sarah Jessica Parker. John Galliano, the British couturier at Christian Dior whose bridal clients include Penelope Cruz, Katy Perry, Gwen Stefani, Gisele Bundchen and Delphine Arnault, the daughter of his boss, Bernard Arnault, the chief executive of the luxury-brand conglomerate LVMH, qualifies with excellent connections as well as enough romantic inspiration to satisfy the ultimate in "most wonderful day of my life" scenarios.
The house of Alexander McQueen, with its blend of English and Scottish heritage, and now helmed by the late designer's former right-hand woman, Sarah Burton, could bring a welcome breath of northern grit, although the fact her first collection for the brand, shown last month in Paris, was inspired by pagan England, might raise the hackles of the Church of England, of which Prince William will one day be Supreme Governor.
Then there is Stella McCartney, who designed the wedding dress for Madonna, still secret after 10 years - a useful precedent for keeping a royal design impregnable - or Georgina Chapman and Keren Craig's deluxe Marchesa label, although the fact this was Coleen Rooney's bridal brand of choice may count against it in the royal wedding stakes.
Whoever the designer, however, several things are certain. The dress will not be short, simple or strapless. Given the religious, historical, ceremonial and global significance of The Day, Kate's gown needs to be sensational and timeless - and with sleeves.
Previous royal wedding designers were yesterday happy to offer advice to whoever becomes Kate's choice.
"I wish it was me, but I wouldn't hold my breath," said Jasper Conran. "You have to think of how the dress looks at any moment, from every angle, and how it will look in 20 years' time. It should not be an embarrassment. It has got to have dignity, so no helicopters!" he said, referring to one of the motifs on the Duchess of York's gown.
"Where the wedding is going to be held will, in some ways, denote the style and shape of the gown," said Lindka Cierach. "Diana was married in St Paul's, which is huge, so she needed a really big gown (the Emanuel design had 100 metres of silk in the petticoat alone), whereas Sarah Ferguson was married in Westminster Abbey, which is smaller. It is important to remember that every stitch, every seam, every bead will be under scrutiny by the world. And make sure you have a private rubbish collection."
"The most important thing he or she will have to worry about is security, because secrecy is the really big issue," agrees Elizabeth Emanuel, one half of the design duo who, along with her former husband, David Emanuel, made Diana, Princess of Wales's wedding dress. "We had to have a huge safe hauled in through the windows of our studio and the dress was locked away every night. We had two security guards 24 hours a day and only one person, apart from David and myself, ever worked on the dress. You have to be strong, well organised, and have a fantastic PR set-up, because this is going to be really, really big. Oh, and whoever it is, they must try and enjoy it, because it really is a wonderful thing to be asked to do."