Kelly Hoppen knows precisely why Donald Trump chose her to design the two penthouses of his flagship Palm Jumeirah project."They came here and said to me, 'Whatever you do - don't sway! Please! Don't make it look like Dubai!'. 'Ha!', I said. 'What? Gold? Glitz? Oh no no no. That's really not going to happen with me'." One thing that Kelly Hoppen definitely doesn't do is glitz. Or gold. Or, even, unless you look very carefully, any colour at all. At some point she became known as the Queen of Taupe. It would be easy to mistake taupe for bland but it is the colour of her success; the Hoppen empire is built on the distinctive inside-of-a-mushroom shade, deviating only into white and off-white, darker browns, greys and black. However, in her most recent London project, she took the radical step of adding a pair of orange velvet chairs. And it is quite an empire: as well as the interior design and soft furnishings businesses, there is a Kelly Hoppen paint collection, a carpet collection, a tap collection, a range for Wedgwood, her London store, her New York store, and her concession in Harvey Nichols in Dubai. Hoppen's selling point is that she has a distinctive, consistent look, yet manages to be many things to many people at once. Just like her favourite colour. More than 20 years ago, she began cultivating her "East meets West" decorating style of bamboo and dark woods, suede and orchids. The exotic yet homely, masculine yet feminine, austere yet cosy look has since inspired interiors all over the world, from boutique hotels to high street shops. She describes her decorating style as "East meets West", a phrase now as over-used in interior design as it is on restaurant menus. But when Hoppen began working her bamboo and dark wood, suede and orchid style more than 20 years ago she was the only one pushing that exotic yet homely, masculine yet feminine, austere yet cosy look that has inspired interiors all over the world, from boutique hotels to high street shops. We meet in her studio (taupe, with occasional accents of beige) in the London area of West Kensington. Hoppen, lithe and wiry, zips around between fabric samples and architects' plans. She wears a bright knitted jacket over leggings and biker boots. Her Titian-hued hair is twisted up onto the back of her head, her nails painted darkest blood-red. The only hint of flash is Hoppen's black Porsche Carrera with its personalised number plate. It is parked inside the building, in front of a wall on which her name has been scrawled in giant graffiti-style letters. Hoppen admits that it's sometimes hard to resist being sucked down by the force of the more-is-more creed that seems to be the over-arching visual code of Dubai. "I actually have to be careful when I'm designing the penthouses that I do not keep thinking it's Dubai. I need to do the opposite. I want to design it as if I were doing, say, a Parisian apartment, and apply the same rules I would to any client anywhere. It's about creating an innate warmth and a sense of home." Johann Schumacher, the managing director of Palm Jumeirah, says that Hoppen's "ability to create a personalised oasis" made her the ideal designer. "Kelly has a relaxed, contemporary style which is a great fit for the overall design of the building," he says. Hoppen says that interior design, like fashion, is now globalised. The pull of trends is as persuasive whether you're in a Hong Kong office or a Cairo apartment. King -Abdullah and Queen Rania of Jordan, Elton John and David and Victoria Beckham are all "Hoppenites". "Taste is no longer limited to a country or climate. People everywhere want the same things," she says. The very act of hiring a designer has become normal, she adds - not dissimilar to hiring a personal stylist for your wardrobe. "It's not like 40 years ago. Now, hiring an interior designer is like going out and buying a pair of shoes." However, the process is a little more rigorous. At the start of every commission Hoppen asks her client to fill in a 50-page questionnaire, in order to learn more about their lives. Questions include: Do your kids get into bed with you every morning? Do your kids have a nanny? Where do you eat breakfast? "Completely essential psychology", she insists. "It's how I work my magic - it's how I make someone a home. It gets very personal: we had one request from a woman who wanted to make sure her side of the bed was nearest the bathroom so that her husband would never see her without make-up". So how is the magic worked when the client is only imaginary, as with the Trump project? The buyers of the penthouses could be of any age and from any corner of the world. But that doesn't matter. Hoppen imagines a client based on the property's price and the marketing projections of the developer. "They could be Indian or Icelandic, Russian or Dutch. The defining point is that they are the type of person who spends the amount of money required to get this kind of property". Designing the Trump apartments has brought "fascinating" demands with the huge amounts of light and the unrelenting, stark backdrop of the desert. "I keep saying to myself, you've got to remember that in these apartments you're up in the sky. "Colour changes in the sky because light changes in the air, and it changes again in different lights in different countries. I'm putting pale, pale colours everywhere that work with the light." Luckily she has been there before - almost. When designing the interiors of British Airways' first-class cabins, Kelly and her team took their materials on a flight to test their suitability 10,000 metres up. Her posture tense with energy, Hoppen hovers over a work table covered in a hundred shades and textures of taupe and swoops on a swatch of loosely-woven beige fabric. "And I'm going to put something like this at the window to let the light in while diffusing it. Otherwise if you're having a bad day you're going to feel pretty awful, no?" Hoppen's first design commission was at 17, for a friend of her stepfather. Work for friends of friends followed, and so it began. In 1996 she won the Andrew Martin International Designer of the Year award and published her first how-to book. There are now six, of which she says, "I'm not bothered about plagiarism - if people are going to do what I do, I'd rather they did it properly." They will also do it for less; the cheapest job she has ever done cost £300,000, she says. Hoppen was born in South Africa and moved to London as a child. She has spoken of how the death of her father, when she was 16, left her with the drive to which she has credited much of her success. Twice-divorced and with one daughter, Natasha, from her first marriage, and two stepdaughters - Sienna Miller and her older sister Savannah - from her second, she bats away questions about her personal life with a practised snap. Yet her decidedly non-taupe -social profile is well documented; her present boyfriend is Nicky Clarke, the celebrity hairdresser. In 2004 there was sniping from the British tabloids when she, then the girlfriend of Sol Campbell, a footballer on the English team, trooped off to Euro 2004 to dazzle obediently with the rest of the WAGs. "I'm a working woman," she protested at the time. Nevertheless, the meshing of work and play does not appear to dull the glow of her empire's progress, and she admits that one of the best things about work is that clients become friends (and, one presumes, friends become clients). A couple of years ago Hoppen felt that she had got as far she could get in her career. She went to David Zelman, an American life coach favoured by Bill Clinton, who had two pieces of advice. First, if she decided to stop she would "fall much further" than she would anticipate and second, she should start to delegate. This, she says, made her career "jump 10 years ahead overnight". Yet only last year did she think she might have found someone to work as an in-house designer. It was not for lack of trying. "People these days just want instant fame. They just want to 'be' - they don't want to learn. But you can't fast-forward it! You have to be prepared to work hard - it's the old-fashioned art of being an apprentice. And it's very hard to find anyone that is willing. You know," she adds, "people have walked up to me and said things like, 'Wow, you've done so well so quickly.' Agh! I'm nearly 50. I've been working on this since I was 17!" Next February, Hoppen will re-start her design school. She describes it as one of the best things she has done in her career and, yes, she's teaching it herself. She did, once, hand the project over to someone else after teaching it in-house but it proved to be a nightmare, not least because the lunches were all wrong. "The whole point of the course is that you enter into our world. That does not mean getting some tacky sandwich in a plastic bag for lunch!" So she pulled the plug. "It was silly, perhaps, because obviously the revenue was good. But I just not could bear it not to be done perfectly." So, for approximately £3,000 you will be able to learn Hoppen's secrets of successful taupe-ness in a week. And have a beautiful lunch. In the meantime, she is moving house again. "I am probably the worst client you could ever have. I'm anxious every day that it's going to work out on time, that I've made the right decision. But that makes me more human - I know exactly what clients will go through in getting to their new homes - and I know exactly how to remove the sting."