'It's been eight years since I've been here,' he says. 'It's changed a lot, but things look good. We've shot in Paris, New York and Los Angeles, so it's time to do Hong Kong. It's good timing because Chanel has a big new shop here and they have couture clients.

'I don't need millions of reasons. I knew I wanted to come here, but I needed a professional reason. Usually I don't recreate a couture show, but here they're capable of rebuilding a set and getting it done. I thought why not? Even without couture I would've done the advertising here.'

Lagerfeld speaks in rapid-fire English (he's also fluent in Italian, German and French), jumping swiftly from topic to topic, dismissing questions that don't interest him.

A charismatic personality, he's also brutally honest. 'May I say something horrible?' he asks. 'I think Chinese women are more handsome than Chinese men. I shouldn't say that, though, huh?'

Image is something that has dominated Lagerfeld's life, both professionally and personally. For the interview, he has gone for a spring look, swapping his usual white stiff-collared shirt for a ruffled burgundy style, coupled with Libertine black jacket with striped panels, and skinny trousers. He is rake thin, with his hands encased in fingerless leather gloves - his mother once told him his hands were 'not beautiful'. Dark sunglasses cover his tanned face, a stark contrast to his powder-white pony-tail.

Lagerfeld is alert, despite having stepped off a plane 24 hours ago. He says this is due to his disciplined routine, which includes abstinence - no drugs, alcohol or cigarettes - and at least seven hours sleep every night.

His diet these days is largely confined to low-fat or steamed food. Once heavily overweight, he shed about 41kg four years ago with the spartan regimen. He has recorded his experience in The Karl Lagerfeld Diet, now a best-seller on the mainland and in Russia. What's more, he has kept the weight off.

'Last night, we had a Chanel dinner at Spoon,' he says. 'It was good, but I ate very little. I only eat steamed fish and vegetables - no butter, no sweets. I have to be very careful because I have to keep my size. It's important in this industry.'

Lagerfeld was born in Hamburg, Germany, the only son of a Swedish businessman who ran a successful condensed-milk empire. His was a privileged childhood, including a personal valet, which he demanded at the age of four. His German mother was said to be a disciplinarian who refused to let him wear glasses (he bought his own eventually and hasn't stopped wearing them since). His father was equally distant. At 14, Lagerfeld was sent to Paris as war loomed and two years later won a coat design award at a contest sponsored by the International Wool Secretariat. Yves St Laurent, who many regarded as his rival later in life, won in the dress category.

'I was always interested [in fashion] before I even knew it was called fashion,' he says. 'When I won the contest, I ended up by accident in something I loved as an idea. But I never thought then that it could become a job and a main element of a lifetime.'

He started out working at the couture studios of Pierre Balmain in 1954 before moving to the house of Jean Patou four years later. After a brief stint as a freelance designer, he joined Fendi in 1967 as a consultant. During the 1970s he made his mark at Chloe, where he designed floaty dresses for its ready-to-wear collections, and a permanent position at Fendi soon followed.

His elevation to the fashion throne came in 1982 when Chanel, which had been in a slump, invited him to lead the fashion house. His mission: to update Coco Chanel's legacy and keep it relevant to the times. Initial reactions were mixed, but each time Lagerfeld made his mark - whether it was with golf-sized pearls, oversized quilted bags, or by pairing Chanel's traditional box jacket with denim miniskirts or tweaking traditional tweed with biker chic.

'You can only be in fashion if you think the moment is the most interesting and most exciting thing that has happened to you,' he says. 'You must fit into times; times don't have to fit with you.

'I'm an intellectual opportunist. It's easy for me to follow time and forget about the past. Personally, I don't have archives. I only work for the present or near future. I don't believe in a faraway future, but I don't believe in the past either - especially not in my own past. For other pasts, things can be addressed for an idea, but my own past I know I have made an effort to forget about it because I don't care about it.

'The world of fashion is changing, and my job is to put Chanel in the mood of the moment,' he says. 'Chanel has to go where fashion goes.'

Lagerfeld's way included a collaboration last year with H&M, making it acceptable for designers to go mass market, although he's adamant he won't repeat the experience. Last month, he again made waves at the New York Fashion Week with two new lines, Karl Lagerfeld and the Lagerfeld collection. They were collaborations with sportswear giant Tommy Hilfiger, which bought his brand last year, and designed simultaneously by Lagerfeld in Paris and a team in New York.

'I was lucky to do it this way. I like the idea of showing in New York, Paris and Milan [with Fendi]. It was a different approach, and the environment and mood made it different. I love to be part of different worlds. That's why I love the worlds of photography, fashion and publishing. I like editorial. I like to be part of what I'm really interested in.'

Among the multiple roles he has undertaken are those of photographer, book publisher and, more recently, guest editor of British Elle. He loves reading and has a library of 200,000 books ('My drama is that I can make no decisions,' he says), owns more than 70 iPods and has an extensive collection of antiques.

Each passion is important to him. 'I love doing what I am doing so much,' he says. 'It's like breathing. You don't ask if you get tired of breathing, you just have to breathe.

'The secret in life is to never compare, never compete. You can't compare my work in publishing with photography and the fashion business - it's all involved and related, but at the same time all separated. But I cannot say I prefer one thing because if I prefer one thing, I should do only that and forget about the rest. I'm lucky to do what I like best, in the best of circumstances.'

At the couture show last week, Lagerfeld was in his element. At the end, he walked proudly along the catwalk with a model, gesturing regally for the audience to rise. At a reception at Shaw Studios, he stands smiling, like a rock star, before the adoring crowd. It's good to be Karl - and he knows it.