As with all weddings, the bride, and crucially her gown, will be the focus of the whole event.

And top designers are predicting that copies of whatever Sophie has chosen to wear for her big day will be available on the High Street the following Monday.

In-house designers for bridal companies are not the only ones showing an over-keen interest in the most talked-about frock since Scary Spice got spliced.

Diana's wedding was watched by 800 million

Samantha Shaw, the designer who was catapulted into the limelight after Sophie commissioned her services for the occasion, and who herself was married last month, has reportedly moved the whole dressmaking operation from her Chelsea studio to a secret location.

The 30-year-old designer - who wears trainers to work and ties her hair up with a pencil - set up her studio four years ago.

She never advertises, and sells her work mainly at private fashion shows - and is as well-connected as her clientele.

Ms Shaw - who is a member of the McAlpine building dynasty - made the wedding dress for Isabella Norman when she married Timothy Knatchbull, Earl Mountbatten's grandson, last year.

Camilla Secil, social editor of Harpers and Queen said: "Sam makes very feminine clothes, very pretty and often layered. She uses very rich fabrics, hand painting and beads."

Elizabeth Emanuel has just launched a new range of wedding dresses

Royal snappers and reporters are falling over themselves to get just the slightest hint of what the frock might look like.

Elizabeth Emanuel, who along with her then husband David, designed the wedding gown of Diana, Princess of Wales, recalls the subterfuge she and her team indulged in to shake the press off their trail.

She told BBC News Online: "We couldn't put anything out in the rubbish, and we had to have our studio guarded by Securicor.

"We used to leave false trails of thread, so that they would think we were using one colour, when in fact we were using another.

Sarah Ferguson's dress had anchors sewn into it

"We had photographers with long lenses occupying buildings opposite ours and we had to take measures to stop them being able to watch us.

"Really, we regarded it all as a game, or we would have gone completely mad."

Lindka Cierach: "Wonderful memories of making Sarah's dress"

Lindka Cierach, who five years later designed Fergie's wedding dress, had to paste metallic covering film to her studio windows to foil photographers' attentions.

She worked "intensively" on the project from her base in Claireville Grove, South Kensington.

She said: "Of course, friends and staff were offered money for information, but everybody was very honorable and I got amazing support from the police."

No hats please

And while Sophie and Edward's do is set to be considerably more low key than either the late princess' or the Duchess of York's, their sartorial stipulations have already been cause for social flustering and consternation.

In keeping with their relatively modern outlook on life, the happy couple are not scheduled to tie the knot until 5pm - which leaves their guests no time to change into something more comfortable for the post nuptial knees-up.

Less traditional still, the couple's invitations request that guests should refrain from wearing hats.

Sophie at Samantha's wedding - but what will she wear to her own?

Instead, they are said to have taken inspiration from Scandanavian tradition, and have invited churchgoers to don eveningwear.

The prince will wear white tie and tails, but of course his bride's confection will not become common knowledge until she sets out for St George's Chapel at Windsor Castle, with the eyes of millions upon her.

Ms Emanuel said: "There were seven or eight hundred million people tuned in to watch Diana's wedding.

"It was not as daunting as one might think because we took a number of precautions. We kept the dress in a safe, and we made a whole separate skirt, which I still have, in case Diana spilled anything onto her dress.

"Diana was an absolutely lovely person - she was just a normal bride, who came along with her mother and thoroughly enjoyed the process of choosing what to wear for herself and her bridesmaids.

Bridesmaids on roller skates

"On one occasion, her bridesmaids all turned up in roller skates. She was very happy and very excited - which is quite normal for a young bride.

"The only concerns we had were that prior to the wedding she lost a lot of weight. All brides lose a bit of weight, but not that much. She went down two dress sizes.

"But she looked fabulous on the day, so beautiful. And at six o'clock she rang us up to say thank you for making her dress. We were very touched by that.

"Sophie is also gorgeous, and Samantha Shaw is a very talented designer. This is a wonderful opportunity for her, and she should enjoy it.