High-street heroes: velvet jeans £35, embellished jacket £70, box bag £30

After reports last week that the great British export will expand to the US, Harriet Walker discovers more about a brand that's thriving

The high street chain River Island has roots in the bomb sites of post-war London, but last week came speculation that the company would be expanding into the US early next year. And with the announcement last month that the store was working on a collaboration with international megastar Rihanna, which will launch next spring, the company seems to be writing its own success story regardless of the recession.

River Island is already firmly established across Europe and Asia, but may yet follow its rival Topshop, which opened a New York store in 2009, and has since expanded across the American heartland. In the US, the concept of the "high street" doesn't exist as it does here, and Topshop's pocket money-friendly take on quirky and cool clothing has proved a hit among young shoppers across the pond.

Although nothing has been confirmed yet, an early season check-in proves that River Island has plenty to shout about: its new collection is stocked full of its own take on the baroque splendour seen on the rather more exclusive catwalks of labels such as Dolce & Gabbana and Moschino for autumn.

Other key influences include edgy youth and street culture, tailored to a customer base that is directional and discerning but keen for a bargain. Prices remain resolutely low, even on items such as shoes and bags that boast thoughtful and complex design features.

"Our customers want fashion with an added twist, and that's exactly what we do," explains Farida Kaikobad, the store's brand director. "New lines go in each week, keeping the stores looking fresh and ensuring customers come back for more. The whole team is very creative and I think this is reflected in our stores – we're often referred to as the 'boutique of the high street!'"

Born as a tiny East London wool shop in 1948, River Island started out as an independent clothing chain across the UK called Lewis Separates, which later morphed into the Sixties high-street hit Chelsea Girl, selling poppy fashion to the teeny-boppers who congregated on the Kings Road. It acquired its current name only in the early Nineties – incidentally, a decade that much of this season's stock harks back to, style-wise.

Having resurrected the Chelsea Girl line in recent years, the company has also added credibility by working alongside designers such as William Tempest, whose line for the brand launches next month, and sponsoring events at London Fashion Week. This season sees the chain hooking up with fashion designers and film-makers too. "River Island is such a successful brand because its style feeds in straight from the street," says Katherine Ormerod, senior fashion news editor at Grazia. "When you're in the stores, you see references taken from music videos, from street style websites and from style icons outside the world of catwalk fashion."

In fact, joining forces with Rihanna came about after the star was spotted out and about wearing several pieces from the store: a simple grey marl T-shirt emblazoned with a Rolling Stones logo; an Aertex mesh cut-out dress, and a pair of barely-there denim hotpants garnered plenty of column inches.

"It's no mean feat when luxury labels are falling over themselves to dress her," continues Katherine Ormerod. "Rihanna is the ultimate street-styler – mashing up insider labels with high street and designer labels, she seems more authentic than many other starlets."

"The River Island shopper is fashion savvy, but not a slave to trends or achingly cool," says Farida Kaikobad. "They all have their own style and shop for either great modern classics or fun seasonal pieces with us."