I don’t suppose you’d guess Peter Högsted was in charge of 10,000 employees and a chunk of one of the world’s best-known and most successful companies. He wears an open-necked shirt and jeans, he swears occasionally, and his office, perched on top of a multistorey car park on a retail estate in Wembley, North London, looks more like a Portakabin than the headquarters of a multi-national. But then the hallmarks of this company are, firstly, a fanatical devotion to cost-cutting and, as part of that devotion, an informal structure. “It’s a very well-regarded, very well-run operation,” says Richard Hyman, an independent retail consultant.

Högsted doesn’t even have the whole Portakabin, merely a desk in the open-plan layout like everyone else. And yet this 39-year-old Dane is the managing director of Ikea UK, which this year celebrates its coming of age in Britain. “Furniture retailing in this country traditionally was not great,” says Hyman. “Ikea has changed that. It puts fashion in the product, it made good Scandinavian design accessible to lots of people.”

“The British in general are extremely laid-back people,” says Högsted. “It’s very easy to talk to British people, they get along and they’re very open to change.” So just as he does not fit the stereotype of a senior corporate man, Högsted’s views on his host country do not follow the usual conservative caricature. But maybe that caricature needs adjusting. In the 21 years since Ikea opened for business here, in Warrington, the British have changed. The middle class has expanded. The boundaries of social class have blurred. The grip of traditional taste, like the top buttons of men’s shirts, has been loosened. Before Ikea, if you had a wine rack you were posh. Now, a wine rack is just somewhere to store wine.

Before Ikea, there was Habitat, but Habitat was never cheap, and consequently it never had more than a sliver, about 1 per cent, of the market. Ikea has about 7.5 per cent, second only to Argos. For a chain with a mere 17 stores, albeit very large stores, Ikea has woven itself into the fabric of British culture, become part of the furniture if you will, remarkably quickly. Like Boots and Smiths in the 20th century, Ikea has become, like Borders, like Gap, one of those places where, in the 21st century, almost everyone shops at some stage.

Given its prices, Ikea has effectively removed personal wealth as a factor for most people in buying home furnishings. This makes Ikea more egalitarian, albeit a great deal less ubiquitous, than Starbucks. £1.50 for a cup of coffee is a lot. £150 for a sofa is not. And if you want a sofa, you do not want to wait three months, let alone until you inherit your parents’. Tory toff Alan Clark once derided the self-made Michael Heseltine as the type of man “who buys his own furniture”. It was a magnificently snobbish put-down, but it makes no sense in a world where furniture is no longer an heirloom supposed to last a century, but a fashion item.

“Ikea is a retailing institution in Sweden, like Marks & Spencer is here, but I don’t know if we can talk about cultural dominance in the UK when we have Argos with 700 stores or DFS with 300,” says Högsted. Perhaps not dominance (the £18 billion a year furniture market is the most fragmented in retailing, with fully 50 per cent of Britons still buying at their local high street shop), but for the young, for the full range of the middle class, for those aspiring to join the middle class, a trip to Ikea has become a modern ritual. Forty-five million customers will enter a British Ikea this year, close on a million a week, more than go to church, more than go to football.

“We know that our core customers are 25-50,” says Högsted, “80 per cent are female, a majority have kids.” In terms of social class, “Bs and C1s are the core”, but Ikea also attracts a lot of what Högsted calls “smart As. They will leave the core furniture items, but they like our kitchens and they will go for kitchenware and tableware and textiles [all to be found in the cleverly demarcated Market Place]. Our customers know what is for me and what isn’t. We are not for the rich, we are for the smart. If you want to use your furniture to display that you are rich, you will not shop at Ikea, but if you are smart it is OK.”

I went down to the entrance of Wembley Ikea and spoke to some customers. Heather Kinuthia, an educational consultant, had come from High Wycombe with her husband and their two young children. She was “looking for storage solutions. We’ve got more and more stuff. The things here are more innovative, more European, more cosmopolitan.” Nicquilla Corbin and her boyfriend Drew McClement, both still in their teens, have travelled from Reading. She works in a dry-cleaner’s, he’s a labourer. “I like it because it’s good taste, good value, up to date,” says Corbin.

Amy Wojcik, a single mother of three from Hemel Hempstead, says, “The kids like coming. They have a hot dog. We’re looking for a bed.” Hussein Majahid, 34, a surveyor, and his wife Mahnaz, 29, a teacher, say: “Our local high street furniture shop has astronomical prices, these are very reasonable.” And so on. These are busy people, hurrying along after work, and none of them seems to have a passionate interest in design. But they do have an interest, more than their parents, I suspect. Certainly, they do not want pelmets or Draylon or chintz. Changing Rooms and its progeny have been on television a long time.

The world over, as people secure the essentials and become wealthier, they tend to spend their spare cash in predictable ways. Clothing and electronic items come first, but once they’re togged up and plugged in, people spend on furniture and interior design. Sweden is a richer country than the UK. The money Britons became accustomed to spending on their homes in the Eighties and Nineties, the Swedes were spending in the Sixties, the Germans were spending in the Seventies, some Russians, and some Chinese, are spending now. And, with 231 stores in 24 countries serving 522 million customers, many of them are spending it in Ikea.

A richer country, Sweden, and also a colder, darker one. For good reasons, the home is historically important to the Swedes. They spend a lot of time in it. “In Sweden,” says Anna Efverlund, an Ikea designer since 1980, the woman who came up with the brightly coloured plastic coat hanger so many of us use, “it is rude not to ask if you can look around when you go into someone else’s home.” Such social mores could only thrive in a far less class-ridden society than Britain used to be.

With a local market willing and able to spend, it is no accident that Ikea started in Sweden, near the small town of Älmhult, to be exact. Getting off the train from Malmö, countless logs from the northern forests passing in the opposite direction, I saw soon enough that Älmhult is a company town. Visitors stay in the Ikea Hotell and Restaurang on Ikeagatan, surrounded by visiting Ikea “co-workers” talking about how great it is to work for Ikea. In the hotel basement are the Ikea archive and the Ikea museum. “Ikea is part of the Swedish soul,” says Görel Karlsson, my guide.

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