LONDON, United Kingdom — Britain's retailers might just be rejoicing as much as Kate and Wills about the birth of a new baby princess.

Baby boutiques, clothing stores and fashion designers received a gift that will keep on giving when the Duchess of Cambridge gave birth to a girl, and all the marketing opportunities she provides, instead of another boring boy, retail experts say. From christening gown to wedding dress, and all the hairstyles in between, every trend the newest royal sets will be fodder for girls seeking to emulate a real life princess.

"The royals having a baby girl is most likely to result in a financial windfall for everyone — U.K. tourism and retailers alike," said Tonya Williams Bradford, a marketing expert at the University of Notre Dame in Indiana. "Unlike with the birth of their beautiful baby boy, where the attention turns to whose next on the throne, this baby girl will provide many style opportunities, as her mother and the late Lady Diana did before her."

Consumers rush to buy all things royal because they are famous in a non-Kardashian way: internationally known but above celebrity. People want to copy what the former Kate Middleton and Prince William — and now their children — are wearing, to touch a bit of that distant gilded glow.

"People, particularly Americans, love it," said Pauline MacLaran, co-author of the upcoming book, "Royal Fever: The British Monarchy in Consumer Culture." ''It's a fascination with a different kind of celebrity."

This goes way beyond commemorative china.

The Center for Retail Research in Nottingham estimated that George provided a 243 million-pound ($368 million) boost to the British economy in the nine weeks after his birth in 2013. But George was the royal couple's first child, the heir to the throne. The immediate impact of a second child will be smaller, about 80 million pounds ($121 million), the center predicted. But the fact that it is a girl opens up a host of long-term opportunities.

This is a princess, after all, a real-life Snow White, Cinderella or Princess Anna from "Frozen."

From the moment Saturday when she first appeared in public with a knitted cream bonnet and every day for the rest of her life, fashionistas will ask: Who is she wearing? A princess isn't just a boon for this year. She's a boon forever.

"It's more fun in general terms and cultural terms when you are dressing up a girl," said Anusha Couttigane, a senior fashion consultant at Conlumino, a London-based retail research firm. "It's just normal that girls attract more attention to fashion."

Couttigane expects the royal couple to continue their practice of using widely available brands from firms even the average person can afford. That's reflected in the white dress Kate wore in the couple's engagement photo — sold by U.K. retailer Reiss, for example. British brands are also likely to do well.

"Kate and William are quite down to Earth royals," she said.

Whatever they wear has extra appeal because the royals don't do advertising. They do grant warrants — a mark of recognition of those who supply goods or services to the Royal Household. Yardley of London, for example, has one for being the manufacturer of toiletry products to the queen.

But it just isn't the same thing as standing before a camera with a bottle of shampoo in your hand. That would just not be done. Ever.

The royals have always been trendsetters. Queen Victoria recognized her marketing power, once hosting a ball to promote the silk industry in east London. Princess Diana was on another level altogether, with every bow or lamb sweater making cash registers ring. That has carried over to Kate who is copied so much that anything she touches is sprinkled with the stardust of the "Kate Effect."

Prince George, the first heir to the throne born in the Internet age, has demonstrated similar appeal.

The swaddle in which George was snuggled in when he emerged from the hospital prompted parents around the world to say: What is the prince wrapped in? Within four hours, the website of swaddle maker aden+anais had crashed. The next day, it crashed again. In nine days, the New York company had received 7,000 orders for that item — a 600-percent increase.

More recently, he appeared in a blue Cath Kidston sweater featuring soldiers in red tunics and bearskin hats. It sold out and then popped up on eBay — at twice the price.

It is time to think pink?

"(Consumers) can go mad over all the girlie things," MacLaran said of princess appeal. "You don't see little boys dressing up in prince outfits, but you see girls do it all the time."

Catherine Hudson, beauty and fashion editor at Prima Baby magazine, said Kate is likely to follow the Countess of Wessex, whose 11-year-old daughter has worn Pale Cloud — a Norwegian brand also popular with the Scandinavian royals.

"I think she will mainly stick to traditional silhouettes ... and, hopefully, continue supporting great British design," Hudson said.

And the marketing opportunities are likely to stretch beyond Britain's borders and outside the fashion choices of the as yet unnamed princess, Bradford said.

"There may even be opportunities as far afield as Disney with their expanding Princess collection," Bradford said. "I believe this opportunity to market the female dynasty of the royal family will truly inspire many market opportunities!"

By: Danica Kirka.