Brands such as Whistles and Barbour cosy up to the likes of MaxMara and Portas's own-line pieces

Mary Portas is a fashion PR-turned consultant and television presenter whose shows, Mary Queen of Shops and Secret Shopper, have taken boutique owners and sales assistants to task for flabby business models and sloppy customer service in a bid to rejuvenate Britain's flagging retail sector.

Now Portas, 51, who has even been asked by the Prime Minister to help revive the high street, has switched sides to open her own store.

When I arrive at Pret a Portas, inside the House of Fraser department store in London's Oxford Street, there is a queue on the pavement and a scrum at the tills. The private express elevator to the shop-within-a-shop is orange – homage to Portas's idiosyncratic hair colour, which the shop's mannequins also sport – and even has a smiling bellboy to push the buttons.

At the heart of the concept is what Mary Portas calls "uncompromising service": there are additional bellboys on hand to help with bags, and stylists, rather than shop assistants, to guide customers through the store, advising and giving honest opinions. If anything should go wrong, there's also a 'moan phone' hotline that promises to deal with complaints quickly.

"I've been working on this for almost five years," says Portas, surrounded by women rifling through rails of silk shifts, structured dresses and delicate blouses. "Most chains neglect women. If I didn't have a designer income, I'd find it very difficult to shop on the high street. I wanted to create classic chic with an edge, an edit of what's out there. Modern women shouldn't be shoe-horned into mediocre fashion."

Portas's selection contains a mixture of high street and designer, with brands such as Whistles and Barbour cosying up to the likes of MaxMara, as well as Portas's own-line pieces .

Prices range from £50 for a blouse to around £300 for a coat – and there are collaborations with several brands that Portas believes are integral to looking good: Radley for handbags, Clarks for shoes, and Playtex for underwear. Add to that a homeware area with scented candles and crockery chosen by Portas herself, and it's a lifestyle bundle that high-street retailers would die for.

"We've had our first customer!" Portas shouts to one of her colleagues as a sale is rung through. "Let's give her a present!"

These are not words often heard in shops nowadays, but Portas's technique harks back a golden age of shopping, when customers were treated as individuals – and individuals who needed to be kept sweet, at that. The customer in question is 50-year-old Angela Ramsden, from Norwich, who caught the 5.30am train to be there for the opening. She chooses a silk blouse for her free gift.

"I really like Mary on telly," she says. "She always looks good, and I find a lot of pieces in the shops look too young. But I could wear virtually anything in here. All this stuff – it's just me."

"Shops still cater to a younger crowd," adds another customer, Kat Brandel, 62, "but they're not the people with money. There's nothing in shops for the over-40s, and Mary is never patronising."

Portas's formula, which manages to combine a large-scale operation with an impressively personal touch, could be just quiet revolution that retailers are desperately looking for in this sluggish patch.

Royal wedding dress sends London to the top

London has been named the fashion capital of the world, and it's all thanks to Kate Middleton and her Alexander McQueen wedding dress, according to an analysis of fashion buzzwords across print media, social networks and the blogosphere.

A growing global obsession with British style meant that New York, Paris and Milan were knocked down to second, third and fourth positions in the Global Language Monitor survey, despite their status as the commercial and creative hubs of the industry. However, some British fashion luminaries expressed doubt about London's rise. The milliner, Stephen Jones, who works with Christian Dior, Marc Jacobs, and Rei Kawakubo said: "For young people, London is the fashion capital, but if you are an American buyer it would be Paris or Milan."

Antony Price, who made his name dressing the pop group Roxy Music, dismissed the survey results as "the usual case of everyone thinks it's 'happening' somewhere else".

"France and Italy have huge clothes companies that act as banks and can properly fund design. In London everyone wants to see a return on their investment in 25 minutes," he added.

But Elle's acting editor-in-chief, Jenny Dickinson, said that London deserved its position at the top. "As much as we feel in our bones that London is the centre of fashion creativity right now, it's always pleasing to have it confirmed. There's no denying, though, that the Duchess of Cambridge's choice of Alexander McQueen's Sarah Burton as a dress designer has been the driving force of this change."

Liam O'Brien