I am standing on a ledge gazing down at the innards of the new Westfield shopping centre in west London. Outside, in the real world, Iceland is suddenly poorer than Africa. Inside, they are preparing for the ultimate shopping experience.

Below the undulating glass roof the site is almost unimaginably enormous – the photographer and I both gasp when we first see it – covering 46 acres and costing £1.6 billion to build. There are nearly 7,000 builders milling about (tip: if you ever want to feel like a supermodel, find 7,000 builders and just stand there).

Westfield, which opens at the end of the month, will play host to 265 retailers, many of whom are building super-duper ultra-alluring flagship stores, from Prada to Waitrose via Nike and House of Fraser. The luxury area alone, centred on a Louis Vuitton shop, is bigger than Liberty. Stores aside, there will be cinemas, bars, restaurants featuring 25 different cuisines, a library, a concert space, a spa, creches, concierges, personal shoppers and a schedule of “arts and educational events and exhibitions for all ages”.

That’s just the tip of the iceberg – I haven’t even mentioned the “cascading stream”, the “wall of lush foliage” or the surreally massive chandeliers.

It is jaw-dropping: I’ve never seen anything like it. It makes malls of the past – Bluewater, Brent Cross, Manchester’s Trafford Centre – look as tired as my titchy spare room. It is also viscerally exciting: gazing out at the acres of shopping possibilities, your shallow little consumerist heart skips more than one beat.

There’s just one little thing among all the gigantism: who’s still shopping? Who, given that the economy may have ceased to exist altogether by the time you read this, is thinking: “I know: I’ll go shopping and spend money I don’t have on things I don’t need – now seems like a good time”?

I can’t think of a single person I know, myself included. When I tell a friend who works near Westfield about the endless lunching options, for instance, she says: “That’s really nice, but I’ve started bringing a packed lunch to work.” Which raises the question: if Westfield is Europe’s biggest city-centre shopping mall, is it also its biggest white elephant?

I love shopping so much that I once wrote a book about it. But even the most ardent devotee can’t help but notice that shopping as we have understood it for the past two decades, from the more-is-more 1980s onwards, is losing its gloss.

It has been coming for a while, and when Philip Green reports a sharp fall in profits, as he did last week for Bhs, you know something is up, despite his protestations. “People are going to go shopping; the world isn’t going to stop,” he said last Tuesday, tellingly equating a downturn in commerce with the end of the world.

Depending on your social class, shopping for anything other than essentials, such as food or school shoes, is either impossible or well on the way to becoming impossible or just about manageable but irremediably tainted by naffness. Certainly, for me, the days of wandering into a department store and thinking, “Hmm, what shall I buy?” are gone; the idea of waving my (hypothetical) new £1,000 bag under people’s noses is just revolting, as well as being the height of unzeitgeisty gaucherie.

I’m not alone: I walked down Bond Street in London last week and every other de luxe store was empty. The glossies may insist that such-and-such is the bag of the season and has a waiting list: that’s not my experience. The bag of the season lay unloved, untouched and unwanted in the shop of the season.

Not far away, in the less luxurious environs of Oxford Street, though, the pavements were as packed as ever. Even those who can no longer afford to shop are still going through the motions: our shopping genes are so well developed that keeping away from the stores is not an option: shopping is what we do.

The danger is that although we set out with the best intentions – window-shopping only, credit card firmly tucked away – clever retailers constantly up their game and lure us in anyway.

To be sure, the high street has a challenge on its hands. This year the cool women I know are knitting and making chutney to give as Christmas presents; their autumn wardrobe comes from charity shops, or from last year, or the year before.

“You know what?” says one designer-loving acquaintance. “I don’t care if my dress is last season. So what? It still looks great, which is why I bought it in the first place. I did buy one thing – a plain black dress from M&S for £25. I’m going to chuck cheap fake jewellery at it.”

Do you often buy dresses from M&S, I ask. “I do now,” she says. “And food from Asda. And one Christmas present per child. They won’t know what’s hit them.”

There is no social embarrassment about any of this: these changes have become a part of life almost overnight. A (male) friend who has been drooling over car magazines for the past six weeks or so, trying to decide which expensive new boy-toy he was going to splash his cash on, has finally made a decision: he will be driving a secondhand Mini – very nice, but not quite the studly hot wheels he had in mind.

“I could still just about buy a flash cartechnically,” he said. “But I have the sickening feeling that I’m going to wake up one of these mornings and get a nasty surprise – so I’m playing safe.”

He’s not wrong: the full consequences of the downturn have still to manifest themselves, which is why Oxford Street is heaving, although sales are slowing.

The end of cheap credit means the cannier people have been quietly mending their spendthrift ways for some time: witness the return of hand-me-downs for children, the longer queues at the shoe-repair booths and the fact that everyone I know seems to be buying a bicycle.

The Chanel counter at Selfridges, I noticed the other week, is no longer packed with People Like Us jostling for this season’s shade of must-have nail-polish: it’s populated by Middle Eastern ladies buying face cream and by a few diehard Wags. Everyone else has gone to Superdrug. Try as I might, I can’t see how this is good news for Westfield.

And yet . . . it’s hard to lose your religion overnight and religion is exactly what shopping has become over the past 20 years: indeed, goods are not just something we worship – they are who we are. If we can’t afford them, we’ll still go and look at them.

We are what we wear, what we carry, what we eat, what we have in our house, what we drive, what we smell like, what holiday we buy – every minute detail of our lives, from how we choose to look to the design of our wine glasses is to do with shopping. Even a community has come to mean Oxford Street on a Saturday afternoon – or Sauchiehall Street in Glasgow, or Briggate in Leeds, or Fargate in Sheffield, or Church Street in Liverpool.

Nourishment or sustenance comes in the form of trainers or dresses or iPods. Rewards equal things you buy, as opposed to, say, lying in bed with a good book. Hopes, dreams, desires, aspirations – all can be attained through shopping, or so we believe. Shopping means that you’re not lonely, but part of a vast community of like-minded people; it also means, handily, that you never have to face your problems.

Feeling down? Reinvent yourself through clothing and accessories. Feeling up? Buy techy gadgets to mark the occasion. Feel there’s a weird sort of hole at the centre of your being? Fill it with goods and the unpleasant feeling will be gone for, ooh, a week or so, which is fine because then it’ll be the weekend again and time for further communion. And so on.

A generation has grown up relying on shopping for identity, because shopping has extraordinary transformative powers: it turns you into the person you wish you were. So even though we may, for reasons of penury or disenchantment or both, recognise that God-as-shopping is the God-that-failed, few people are going to be able to sever all ties overnight; my canny girlfriends aren’t necessarily representative of Mrs Smith in Bradford, who still needs a “treat” because “she’s worth it”.

Ergo, although Westfield may seem like the equivalent of building a giant cathedral just as the news breaks that God doesn’t in fact exist, it doesn’t follow that the cathedral will be empty, or even half-full.

Shopping goes through us like the writing in a stick of rock and there are hundreds of thousands of people out there who won’t let lost deposits or unemployment or spiralling mortgage repayments stand in the way of their fix. The malls are still packed: last weekend Brent Cross was heaving, Bluewater was crammed.

Are they buying? Not necessarily. But they’re breathing in the artificially fragranced air and peering into windows and believing – because that’s what shopping does to you – that their husband would love them again if only they bought that set of lingerie, that their bickering family would turn into the Waltons if they forked out for the organic chicken, that the office Christmas party won’t be the usual miserable nightmare if they swallow hard and hand over the cash for the beautiful dress, that they’ll write that bestselling novel if they buy the laptop.

Shopping is all about the money. Despite what retailers say – that they understand the economic climate (how could they not, when it must rise up and punch them in the face every morning?) and are willing to brave it out – shop owners and backers must be hyperventilating with panic, Westfield’s included. As for the rest of us, it’s complex: shopping cuts to the very core of our being.

If a massive new mall claims to understand, to welcome us in despite our empty pockets, to soothe us with valet parking and provide us with excuses – “there are food shops in there, I’ll just go and buy some veg”, “I need a box of paperclips and a reel of cotton” – then many of us will find ourselves powerless to resist.

Shopping is about glamour and escapism and even broke people – especially broke people – need their glamour fix: that’s why shopping centres are still packed at times of day when employed people are at work. Gigantic supermalls provide it by osmosis: just wandering around in its blond wood and gleaming glass and marble floors makes you feel as if you are Carrie in Sex and the City, not some exhausted drudge whose bills seem to be spiralling out of control.

A spin round Vuitton, a nose round Zara, a latte on the terrace, and you are your fantasy version of yourself again, ready to face the rest of the day. Shopping is dead. Long live shopping.

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