Meghan's wedding dress...
US actress Meghan may also opt for a dress from her adopted country to curry favor with the public and to boost Britain's valuable fashion industry.
There is also some speculation, although far less, about what ex-army man Harry will wear on his big day -- a civilian suit or a full dress uniform?
Prince Charles will walk Markle down the aisle during her marriage to his son Prince Harry after her father pulled out of the ceremony for health reasons, Kensington Palace announced Friday.
"Ms Meghan Markle has asked His Royal Highness The Prince of Wales to accompany her down the aisle... on her wedding day," said a palace statement.
"The Prince of Wales is pleased to be able to welcome Ms Markle to the royal family in this way." Whimsical, traditional, or both? London has been buzzing for weeks with rumors about who will design Markle's dress, with Burberry, Ralph & Russo, who had made Markle's engagement dress, Stella McCartney, Erdem, Alexander McQueen, Antonio Berardi and Roland Mouret all being mentioned.
Mouret told AFP in February that he wouldn't reveal if he was the chosen man, saying: "She's a friend and the great gift I can give my friends is to keep their lives private."
Fashionista Markle told Glamour magazine in 2016 that her ideal outfit would be "very pared down and relaxed."
"I personally prefer wedding dresses that are whimsical or subtly romantic," she said.
But by marrying into the royal family, Meghan is also joining an institution whose traditions will impose their own restrictions.
"From Honiton lace to Orange Blossom, Royal Wedding Dresses over the years have encompassed tradition, whilst still embracing changing fashions," the family's official website said of its approach to the gown.
British Fashion Council chief Caroline Rush believes Markle will strike the right balance.
"Throughout the past couple of months, Meghan Markle has proved to be very considered in her choice of what she wears," she said.
"She understands the subtle power fashion has in terms of challenging conventions, connecting to a community but also putting local companies in the spotlight."
Meghan's previous marriage to film producer Trevor Engelson also throws up a complication, raising the question of whether she will be able to wear white.
"The etiquette on white dresses for second marriages is now very fluid," wedding dress designer Raishma told the Daily Express.
"However, she is marrying a member of the Royal family, so she may opt for ivory or an off white shade which actually would be perfect on her skin tone."
International exposure
One thing for certain is that the designer will receive a worldwide boost from the exposure that only a royal wedding can provide.
The ceremony will be beamed into homes across the globe, with the audience expected to be at least tens of millions.
Moments after it is first unveiled, the dress will be analyzed from every possible angle by websites who provide links for those looking to recreate the wardrobes of the famous.
But it is not only Meghan's choices that will affect the fashion world.
"The royals have been influencers long before the term even existed," explained Sam Coates, a PR expert based in London.
"No matter what your thoughts on the royal family, they can certainly propel a brand to fame."
Markle and the Duchess of Cambridge have both chosen to wear high-street brands in the past, heralding a shift in the industry.
"These accessibly priced pieces sell out in seconds," he said. "My view is that this is a great opportunity, for both emerging and established brands to gain exposure on an international level."
Windsor in lockdown
On the eve of the royal wedding, the picturesque town of Windsor seemed like an impregnable fortress.
Every nook and cranny has been scoured and every imaginable security measure deployed to guarantee the safety of the royal couple and the tens of thousands of spectators set to flood the streets.
Huge barriers have been hauled into place to prevent a vehicle attack and many roads are now closed in the town of 30,000 inhabitants, 30 kilometres (19 miles) west of London.
Number plates are also being automatically scanned and surveillance cameras have been deployed en masse.
The wedding is expected to attract around 100,000 spectators in Windsor itself, with at least 5,000 journalists, according to Thames Valley Police.
"A broad range of visible security measures are in place," a spokesman told AFP.
On D-day, train stations will be on high alert, vehicles will be inspected and visitors can expect to be searched.
No drones will be allowed to fly over the wedding zone.
For the royal couple themselves one of the greatest risks is their open-top carriage procession.
"Things can go wrong whenever you have big crowds of people," Chris Phillips, former head of Britain's counter-terrorism security office, told AFP.
"You can make sure there's no room for snipers and things and just don't let people to get too close to it. It's the key," said Phillips.
Totally eliminating the risks on the day is an impossible task, but police have assured residents "there is no intelligence to suggest that the event is a target".
Local councils have also deployed dozens of "ambassadors", volunteers who will guide visitors but also act as extra sets of eyes and ears on the ground.
The number of police set to guard the ceremony has not been disclosed, but is "probably at least thousands", according to Phillips.
That is to say nothing of the cost of the security, which will be billed to the British taxpayer.