She rarely talks in public, is appalled by the idea of joining Twitter and yet her sinewy bow legs and the mole on her breast are instantly recognisable on their own terms. The woman, whose mantra is "never complain, never explain", which former boyfriend Johnny Depp is said to have advised her to live by, is unquestionably the most famous model in the world.

Kate Moss, the daughter of a barmaid and a travel agent, turned 40 on January 16 and although she has been the object of our gaze for 25 years, she shows no sign of losing her place at the top of the most fickle of industries.

Despite her immense wealth - between October 2011 and October 2012 her wages totalled £11.72 million (HK$150 million) - and her recent accolade at the British Fashion Awards in recognition of her extraordinary contribution to the British fashion industry, there are no signs of early retirement. Moss chose to celebrate her 40th birthday with a shoot in Playboy, for the magazine's 60th anniversary edition, wearing the full bunny get-up - silky ears, bobtail and cuffs - and shot by top fashion photography duo Mert & Marcus. The Mail Online website thigh-rubbingly described the 18-page shoot as "showing off her razor-sharp cheekbones, and her still slender figure". The semaphored message from inside the impenetrable Moss camp was: Still Got It.

But 2014 will not just be about modelling for Moss. She will reprise her role as designer at multinational retailer Topshop. She will become the first model to appear on British Vogue's masthead as contributing fashion editor. Her first shoot will appear in a spring issue and, according to insiders, the photographs will genuinely represent Moss as a working fashion editor rather than depicting the ghost-styling work of someone else.

Alexandra Shulman, the magazine's editor, says: "She came in recently to go through her rail for her first shoot and what I realised was that when she talked about the clothes she completely understood what it was about each item that makes it special. She could show some-thing which you felt indifferent to, but when she talked about each item you see them in a different light. All good fashion editors can breathe life into a rail of clothes, but it is unusual for a model to be able to do that. To see that made me optimistic about what she will be like as a stylist."

Moss wasn't born to be a modelling legend. On paper, with her snaggle-tooth and her 1.73-metre frame, the odds on the 14-year-old from Croydon, south London, enjoying an unparalleled catwalk career were stacked against her, particularly as "Amazonian supermodel" was the aesthetic at the time she was spotted. But a chance meeting with model agent Sarah Doukas at JFK Airport, New York, in the United States, catapulted her from schoolgirl to the model who has appeared on the cover of British Vogue 34 times - more than anyone else.

It is a turn of events that Moss admits surprised her. She said recently, "I was, like, a child when I started. I was 14. If it hadn't happened, I don't know what would have happened to me. I would be in Croydon working in a bar probably."

Nonetheless, she welcomed the opportunities the fashion world afforded her. She told Welsh crooner Tom Jones in the interview for Playboy in December, "I wanted to be at the centre of things. I love working with creative people and there was none of that where I came from. As soon as I was given a chance I took it."

For most, 25 years in the same job is either a stunning achievement or evidence of a career resting on its laurels. The fashion industry doesn't tolerate the latter and Moss has proclaimed that she doesn't "do boredom" but somehow she has managed to stay relevant. Her ability to morph with the times runs counter to the modelling careers of others whose features became so closely linked with an era, such as Marie Helvin in the 1970s and Cindy Crawford in the 80s. Moss' features were once associated with the waif look of the early 90s; she represented the girl next door rather than an otherworldly beauty. A photograph of a topless Moss running down a beach wearing a feather headdress, taken by Corinne Day and appearing on the cover of The Face magazine in 1990, symbolised a turning point in the fashion industry.

Marc Jacobs, designer and friend of Moss, says of their meeting during this period, "About 2½ decades ago, I was mesmerised by a Corinne Day photograph of the most uniquely beautiful and imperfectly perfect girl I had ever seen. Shortly afterwards, Kate and I worked together for the first time. It was my grunge collection and while that show marked the end of my [clothing brand] Perry Ellis career, it began what is one of my most cherished and special friendships."

Shortly after this, however, Moss' look became associated with something more sinister: heroin chic and the glamorisation of anorexia. It marked one of the low points in her career. Moss has tried to distance herself from both harmful associations. "I had never ever taken heroin," she has said. But her infamous quote in 2009 to fashion news website WWD that her motto was "nothing tastes as good as skinny feels" didn't help her reputation. In a rare interview with Vanity Fair in 2012, she appeared to blame those around her for her bony frame in the 90s by explaining "you don't get fed".

For the past 10 years her appeal has centred on her "get-the-look" paparazzi-friendly wardrobe and the perception that she is having the most fun in the world, whether it is cackling on the beach in a bikini with cigarette in hand or emerging from a VIP party with her rock 'n' roll blonde locks perfectly dishevelled.

Shulman believes the secret of Moss' relevance is "probably glamour".

"I always thought glamour involves an element of unpredictability and unruliness and I think you can apply that to Kate. It isn't simply that she is beautiful, it is that she is glamorous as well."

Her reputation came briefly unstuck in September 2005, when the London-based Daily Mirror newspaper ran photographs of her apparently taking cocaine. She was never charged and although she lost contracts initially - Burberry, Chanel and H&M dropped her after the scandal - both designer brands have since employed her. Neither her earnings nor her reputation have suffered in the long term.

Critics of Moss are hard to find among those who know her. Off the record, some insiders claim that she can be "quite spoilt" and, more tactfully, that "she knows what she wants". But the Kate Moss circle is tight. Loyalty and silence are the watchwords among her friends. Tellingly, she still hangs out with many of the same friends and colleagues she has had throughout her career - publicity agent Fran Cutler, hairdresser James Brown and disgraced designer John Galliano.

The latter designed Moss' wedding dress for her marriage to The Kills musician Jamie Hince in 2011, when the rest of the industry was keeping him at arm's length. Doukas remains her agent, but as a spokesman explains, "Sarah is very involved with managing Kate's career, but she rarely discusses Kate in public."

Moss' loyalty is repaid by their confidentiality. Shulman says, "You talk to her friends and they adore her. I can only imagine that her loyalty to them plays a part in that."

On-the-record Moss talk is easier. Make-up artist and long-time friend Charlotte Tilbury has said of Moss' face, "She is a make-up artist's dream, with her killer cheekbones, heart-shaped lips and incredible almond-shaped eyes." Photographer Tim Walker says, "She has such a joy for life. You have never met anyone with such a sense of living 100 per cent in the moment."

Meanwhile, Jacobs describes her as "not only a fashion icon, she embodies the spirit of London. She is a woman of incomparable style."

The fascination with Moss is destined to continue, with industry watchers and fans looking forward to seeing what her one-off collection for Topshop (the Hong Kong branch of which is at 59 Queen's Road Central) will be like this spring. Insiders are already proclaiming it to be better than the 2007 collection. But as ever, it will be her actions more than her words that keep us in thrall. Tantalisingly, Shulman says, "She doesn't talk in public but she talks non-stop in private. She is garrulous and cracks jokes non-stop. To be so disciplined and restrained about saying anything in public is such an interesting mix."

Moss says she is not ready for full disclosure, with no autobiography planned as yet.

"Not until I'm, like, 105. Because you can't get a good book unless you're going to spill the beans, and I can't spill the beans … not for a long time."

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