So what will Meghan Markle wear for that walk up the aisle?
As that wedding draws closer, royal watchers everywhere are wondering if the former actress will stick with tradition and a British designer or go for something more left field. Karen Dacre gets the views of fashion insiders
The next time the UK is invited to add a sport to the Olympics, Royal Wedding-dress guessing may be a worthy contender. Certainly, making predictions about the length, shape and designer of the gown that Meghan Markle will wear this Saturday is family-friendly entertainment that has proven its ability to captivate the attention of the UK.
From journeys to work to water cooler conversations, the Mystery of Meghan's Dress rolls on with us, a nation brimming with spoiler addicts, outraged by the idea that we must wait until Saturday to see how this one ends. In my royal wedding fantasy, a slightly hungover Meghan Markle combines bed head with smudged eyeliner and a Céline tuxedo before heading (by chaffeur-driven Defender) to Windsor Castle. There she greets her girl gang with a group hug and a flurry of Instagram activity before walking down the aisle to the sounds of The National's England.
Then reality and the deadweight of history descends, and I realise a pretty but conservative choice is a dead cert. The trouble with marrying into the monarchy (I've heard) is that protocol trumps playfulness, which means that whatever Meghan chooses will have a decidedly somber tone. A gown by Roksanda Ilin-cic is the perfect way to bridge the gap between contemporary cool and palace-worthy attire while flying the flag for British style.
With speculation still rife (first it was Erdem, then it wasn't, then it was Stella McCartney, then it was definitely Erdem, then it was Ralph & Russo and then ... you get the idea) and the notoriously tight-lipped powers-that-be at the Palace offering nothing but poker faces when quizzed on the issue, it falls to the fashion industry to add fuel to your fun.
Here we ask the experts for their predictions. What larks. And they say there are no prizes for guessing.
Edwina Ehrman, senior exhibition curator at the V&A
For me, it's Ralph & Russo. The bride is already a client, and wise brides go to people they trust. They are London-based couturiers with the design expertise, in-house skills and networks to create a dress as elaborate or simple as the bride wishes.
Ms Markle is marrying into an environmentally conscious family and couturiers can offer a transparent and traceable supply chain, and source very specific materials. Traditionally, couture garments are made with generous seam and hem allowances to enable alterations and are designed with the future in mind, whether that is for long-term wear in their original form or to be transformed into an equally finished outfit from which the wearer will gain more use.
Any spare materials remaining after the dress is made will be given to the bride to use in the future to mend or alter the dress, or even perhaps to create something new but with incredible memories.
The menswear expert
Teo Van den Broeke, style and grooming director, British GQ
The shape of Meghan Markle's personal style is surprisingly difficult to define: this makes it difficult to determine exactly what she'll wear on the big day, it doesn't mean we can't speculate about the brand she might choose. For my money she'll go British.
This is a prime opportunity for Markle to get the UK press corps fully on side, so if she's clever she'll play it safe with Erdem or Vivienne Westwood. More exciting, however, would be if she decided to go a bit avant garde with her choice.
A cream couture coat with a tulle portrait on the front by John Galliano for Maison Margiela, for instance, or a silk and lace baby-doll dress by Simone Rocha.
The dream? Meghan Markle squeezing down the aisle at St George's Chapel in Windsor wearing a multi-layered taffeta dress by British designer of the moment, Molly Goddard.
That said, she could just blow it out of the water and wear the first-ever Riccardo Tisci for Burberry look. Now, that would be something.
Elizabeth von der Goltz, global buying director at Net-A-Porter
I would love to see her in something that has the "wow" factor and really marks the occasion of her becoming a princess. But also something quite modern because she represents so much for women today: she comes from a multicultural background, was a successful actress and had a strong career so I hope this shines through in her choice of wedding gown.
I would love to see her wear something by an American designer leading up to the big day but I am quite sure she will be in a gown designed by a British designer for the actual royal wedding.
However, I do think her choice will be less traditional than previous dresses we've seen from royal weddings.
The beauty boss
Sharmadean Reid, founder of WAH Nails and BeautyStack
I think it would be great if Meghan eschewed the big and lacy for something sleek, like a simple off-white silk bias-cut gown like something out of Sex and the City. Rose quartz nails are huge in the salon for weddings still - she could experiment on her nails.
The style plate
Caroline Issa, fashion director and consultant
I hope that Meghan supports young British talent and wears a modern wedding dress by someone like Grace Wales Bonner, something with a sharp silhouette, thoughtfulness put into it and a real love and fulfilment of craft. Just as the Queen put youngster Richard Quinn on the map, Meghan could really put Wales Bonner on the global map.
Saying that, I'd also love to see her in either a Temperley London creation or Erdem - both with different but equally relevant feminine takes on "wow" dressing.
Pandora Sykes, journalist and co-host of podcast, The High Low
Whereas with Kate it felt quite obvious who she would wear - at that time, Sarah Burton was the name on everyone's lips both in the industry at large and in reference to the royal wedding - I think it's more likely that rather than "go British", Meghan will go with something high in the glamour stakes.
She doesn't have the same obligations on her: it isn't a royal wedding of the same diplomatic importance. She's much more international than Kate - more red carpet than grouse moor. I expect she will wear Ralph & Russo again.
She strikes me as a bustier girl, but will probably have to cover her shoulders, so my bet is on tight long sleeves and a lace V. A sort of slinked-up version of Kate's perhaps. In another world, I could actually imagine her wearing Marchesa.