Vanessa Friedman • New York Times News Service

Royal watchers, fairy tale lovers and proponents of the “special relationship” between Britain and the United States, let out your collective breath: Prince Harry, fifth in line to the British throne, famous flirt, recent spokesman for mental health and all-around paparazzi magnet, and his girlfriend, American actress Meghan Markle, are engaged. And the British royal family has officially entered the 21st century.

If the marriage of Prince William and Catherine Middleton was a rare instance in which a commoner wed the heir to the throne, this royal wedding will herald the Windsors’ (relatively radical, if expected) embrace of a divorced and biracial American. And you know what that means!

Not just that she will redeem the legacy of Wallis Simpson. But that she will become a symbol among symbols: one of the most-watched, obsessed-over women outside Hollywood. And like so many of the women who marry into the royal family, she probably won’t be heard very much but will often be seen, so what she wears is suddenly going to matter, and be chronicled, a whole lot.

The British fashion industry, on tenterhooks as it awaits the various outcomes of Britain’s exit from the European Union, must be rubbing its hands in anticipation. Oh, the clothes her patronage can potentially sell!

It has already started.

The belted white coat that Markle wore for her official engagement appearance with Prince Harry outside Kensington Palace last week, by the Canadian brand Line the Label, set off a frenzy that was said to have crashed the website within an hour. (The brand is said to be renaming the coat “the Meghan.”)

And there is a blog — Meghan’s Mirror — that chronicles her every style choice. Vogue has a piece online titled “Meghan Markle’s Stealth Shopping Style Is All the Black Friday Inspo You Need,” while InStyle crowed “The Nordstrom Black Friday Sale Has Discounts on Meghan Markle’s Favorite Denim Brand.”

If she does that for jeans, just imagine what she could do for, say, day dresses — like the forest green frock with a bow at the waist from Italian label P.A.R.O.S.H. she wore for her BBC post-engagement interview (for those who don’t know the brand, which is probably most people, the name stands for Paolo Rossello Second Hand, Paolo Rossello being the designer and second hand referring to the fact the line began by repurposing vintage garments). Along with whatever protocol lessons she is taking, she is going to have to decide what kind of style setter she wants to be.

Just consider the fact that not only does Catherine, the Duchess of Cambridge, tend to create an immediate buying frenzy for anything she wears, but so do her children: Prince George and Princess Charlotte. Consider that, with Theresa May in 10 Downing St. rightfully focusing attention on what she negotiates more than on the shoes she wears, there is no first lady equivalent à la Samantha Cameron, to boost the local fashion industry through appearances and strategic styling, thus upping the spotlight ante on the new-gen royals.

And consider that unlike Markle’s future sister-in-law, who has been adept at walking the very fine fashion line between classic and accessible with her patronage of brands from the high-end (Jenny Packham and Temperley London) to the high street (Zara, Topshop, Reiss), always with a sensible pump (often by L.K. Bennett) and de rigueur sheer stockings, Prince Harry’s bride will have a certain leeway. She can be more adventurous, less strictly appropriate.

That is both because her future husband is further from the responsibilities of the throne, and because the expectations surrounding them are different: their job, to a certain extent, is to push boundaries; to be even more relatable and modern than are Catherine and William.

I mean: Markle did wear ripped jeans (ripped jeans!) to sit near her future husband at the Invictus Games in September in Toronto. It caused a hoo-ha, but as she began, so she may continue. Just imagine the big step forward she could take with bare legs. Certainly, the strappy Aquazzura stilettos she chose for her engagement debut were more daring than Catherine’s trademark footwear.

Will she choose to champion certain British designers — perhaps, like Michelle Obama with American ones, the edgier and up-and-coming (Simone Rocha? J.W. Anderson?) — the better to promote them around the world and show her loyalty to her new country? Or will she underscore the values of cross-border relationships in the face of British isolationism, and work with some names from the United States? Those famous jeans were by the Los Angeles-based brand Mother, known for producing its denim in the USA. Presumably, though she wore some Canadian brands while filming the television show “Suits” in Toronto, as she did last week with LINE, she won’t regularly continue, though it’s possible the fact she did not choose a U.K. designer for her engagement look is telling. Will she work with a single designer, or spread her favor?

Burberry is about to name a new creative director (rumor has it that Phoebe Philo of Céline is the favorite). A new designer for a new royal, both fresh faces in heritage houses, would make for a very nice narrative. Or there’s Victoria Beckham, another barrier-breaker, who moved from frothy pop stardom to designer substance, and could be a kindred spirit when it comes to crafting an image.

We will see — perhaps the front rows of London Fashion Week in February, where Markle will unquestionably be the most-desired guest for any brand, will provide a clue. Still, the first real statement as to where this is all going will be the wedding dress. There is a lot riding on the choice.

When Catherine opted for a gown from Sarah Burton for Alexander McQueen (one of the best-kept secrets of 2011), it spoke of her desire to support both a woman and a newish British brand, and it started an on-off partnership between the duchess and Burton that has continued to this day, and helped recast McQueen as more than just a high-fashion name known for intense creativity and a dark past. When her sister, Pippa Middleton, chose Giles Deacon as the designer of her wedding look in May, it likewise set off a frenzy of Deaconophilia.

Both women opted for Grace Kelly-like, lace princess confections, marked by simplicity and an implicit reference to that famous wedding past, with all its cinematic romance.

Markle has a chance to chart a new course via her dress, one that is perhaps a little more contemporary and a little less spun sugar. One that says to the millions who will be watching: This is the way I am redefining how it looks to be royal. Markle is someone who implicitly understands the power of dressing the part, so surely this opportunity has not escaped her.

Here’s hoping she seizes it.

18903733