The devil may wear Prada, as long as Vogue says it's OK

Fashion fickle? Its 'bible' is celebrating 90 years of thriving on the same formula, Alexandra Shulman, its British editor, tells James Robinson

Never mind the furore over 'size zero' models, Kate Moss's new career as a designer, or the hype surrounding Vogue's 90th birthday celebrations this week. There are two questions that demand an immediate answer from the magazine's editor, Alexandra Shulman. First, what did she think of The Devil Wears Prada, the film based on the book by Lauren Weisberger, a former intern at American Vogue? She says she found it 'very funny. Parts of it resonated. It wasn't completely unlike the existence here.'

Indeed, in an uncanny example of life imitating art, Shulman arranged for her own assistant Sacha to write a piece for the Daily Telegraph about her experience of working for a real-life fashion magazine editor - a task which she approached with understandable apprehension.

'Poor Sacha. She was in a terrible state,' laughs Shulman, who refused her assistant's repeated requests to read the piece before publication. 'It wouldn't have been right, although I knew she wasn't going to do a hatchet job on me. I'm not stupid.'

The second question is why, after 10 years, Shulman has decided to take her column from the Daily Telegraph to the Daily Mail. She is the latest big name to swap sides in an escalating talent-poaching war between the two newspapers. Money seems to be the obvious answer, but industry sources say that isn't the case. They point out that Shulman has a good relationship with Sarah Sands, the former Sunday Telegraph editor, who is now an executive at the Mail

The British edition of the iconic magazine, founded in New York but launched in the UK at the height of the First World War, celebrates its 90th anniversary this week with a bumper edition featuring the best of issues past. The page proofs arrive as we sit in Shulman's spacious office and are every bit as sumptuous as you would expect.

Stunning Mario Testino and David Bailey photoshoots and generous full-page tributes from designer brands sit alongside contributions from famous names in music, the arts, literature and, of course, fashion. There is also some great writing, including a piece by Truman Capote, Seamus Heaney on New York and Richard Burton on travelling with Elizabeth Taylor ('a kind of exquisite pain').

As ever, it is crammed with advertising, which is why Vogue remains Conde Nast's biggest money-spinner, despite successful launches of magazines such as Glamour and Easy Living

Shulman, always opinionated but famously unpretentious, has increased circulation to 216,000 in her 14 years in charge, the highest ever. 'Something's going wrong if it's going down. I see that we should only go up,' she says.

If that sounds like a publisher's dream, so does her punishing work schedule. 'This is my life,' she shrugs. 'I see it though completely rose-tinted glasses.'

In some senses it is a job she was born to do. Both her parents were writers and Vogue was a fixture in her childhood home in west London. 'You could only dream about being the girl in Vogue,' she remembers, though she did once appear in the magazine; the photo of her younger self sits in her office. 'Vogue depicted a glamorous existence, although it never seemed entirely unachievable.'

That is the idea, of course. No other magazine is as unashamedly aspirational or elitist. Others, such as upstart bi-annual Pop, may be more fashionable, but Vogue sets the tone, and Shulman wields huge power in the fickle world of fashion.

There is no shortage of unflattering anecdotes about 'Conde Nasty', however, many of them told by former employees. One recalls seeing the acronym NTF (no trust fund) written on their CV, presumably to remind human resources that they should be first in line for a pay rise.

Should a new version of one of those tacky office signs be placed in the foyer, I wonder, reading: 'You don't have to be posh to work here, but it helps?'

'No,' Shulman insists. 'Things have changed as the company has become bigger. It's a lot more egalitarian.'

Shulman began her career at Tatler, later taking charge of GQ before getting the Vogue editorship in 1992. Since then, she has enhanced its reputation as a 'fashion bible', and raised its profile. But in many ways, she says, flicking through the proofs, it hasn't changed that much in 90 years: 'The ingredients have remained the same; fashion, beauty, social observation, the arts.'

Her decision to expand the fashion coverage by introducing high-street clothes at lower prices, will probably prove a lasting legacy. That was prompted in part by competition from Elle and Marie Claire, but it was also driven by industry trends.

'Top Shop has been hugely significant. Philip [Green] knows what he's got and knows he will have to keep on supporting fashion. But Terry Green started it all with Designers at Debenhams some time ago. Even [cheap chic chain] Target in America signs up the designers now. We are more interested in design, style and fashion. The number of people who recognise designer labels is amazing.'

Shulman is characteristically frank about the nation's apparent obsession with shopping: 'I think shopping's great. It's not the only thing in the world, but it's fun. I'm hugely motivated by consumerism. I don't think I would have ever got up in the morning if I hadn't wanted to buy something. I think it brings people pleasure.'

She also defends the British fashion industry, which is sometimes portrayed, most recently by the Evening Standard, as a hellish netherworld where underage anorexic models are force-fed cocaine.

'I rang [Standard editor] Veronica Wadley from the [London Fashion Week] shows because so many of the girls were saying "We're being harassed by the Standard". We had a heated debate.' It ended with the Standard running a lengthy quote, but the argument raged on long after the week was over.

'It is a really complex question,' says Shulman, who points out that - unlike other titles - Vogue does not publish diets. 'Of course, girls should not be sick. Anorexia is an awful illness. Some people - not just models but actresses and celebrities - exacerbate the situation, but Jean Shrimpton and Twiggy were not fatter than Lily Cole or Kate Moss.

'People are motivated by what they can't have. Centuries ago, being slightly plump was a sign of prosperity and status. Now it's the reverse. Is it rational? No, not really. But it was ever thus.'