Financial wizard Ivan Massow has made his fortune by defying old prejudices. His new London home reflects a brave approach to living, too. By Oliver Bennett. Photographs by Richard Glover

hen I meet Ivan Massow, he has just returned from St Tropez and has arrived back in his Mayfair mews house. St Tropez? Mayfair? Is he single-handedly trying to revive the 1950s playboy circuit? "Mayfair has been overlooked," he says. "It's under-priced because it's so horribly unfashionable." This is bound to change, if Massow's previous enterprises are anything to go by.

Massow is the 30-year-old whizz-kid who realised a few years ago that insurance companies were financially discriminating against gay investors, particularly those with Aids and HIV. He started to broker for these clients and has become "one of the largest providers in the industry". Now the firm has expanded beyond the core pink-pounders into "metropolitan people who want to plan for the weekend as well as retirement" - such as the heterosexual couple who came in recently, angry that another advisor had assumed they were going to have children.

This timely non-conformism has made Massow a rich man - "I certainly don't feel like a millionaire, though I'm always being described as one." He is also perceived as something of a financial seer, with a profile as a talking head on television, clearly helped by good looks (he was once a model, a profession about which he is now scathing). And now he has a new mews house: a Piccadilly pad of the sort that Austin Powers would die for.

It is important for Massow to be central, as he walks to work in Cambridge Circus and he likes being close to Green Park, where he can take his dog. He moved from Soho, where he lived in an early Georgian house, and had considered staying within the area. But, for him, Soho has lost a lot of its charm: "It's full of bridge-and- tunnel types crowding into theme pubs and chain cafes." There is also its low-life aspect: "The Zero Tolerance policy in King's Cross has passed a huge drugs problem on to Soho. But I object to the sleaziness far less than I do to the Pitcher and Piano." There were other considerations. One was that he was annoyed with English Heritage, who, he says, stalled the improvements on his previous flat. "You get the feeling they would prefer that old buildings decayed." But the key factor was that his live-in partner, James Knight, 24, committed suicide nearby after suffering depression. "I couldn't move for ages because it was always his place," says Massow. "Moving here was about moving on ... getting back on the rails." The new house is minimal and uncluttered; contemplative and reposed. "I've never had anything like his before," says the naturally acquisitive Massow. His possessions crowd out his farmhouse in Sussex and his new Queen Anne mansion in Somerset, but this place has to stay calm.

alk in from the cobbled courtyard and an all-white, and, frankly, mausoleum-like stairwell takes you up to the door. Once inside, it is warmer than expected, with carpet and cherrywood used throughout the first floor. Even so, Massow had to argue his case with the vendors, who also helped to arrange the design. "They wanted heavy minimalism: white, chrome, and that green etched glass everywhere," he sighs. "But as I lived with my dog and wanted a home not a show flat, I needed it to be softened slightly." He collaborated with the interior designer Ben Mathers - who also refurbished Massow Associates' new office - to make it less austere, though the upper floor is more showy, consisting of a large converted loft-space, with "plenty of space to pace around" on handsome limestone floor tiles. "They look beautiful, like marble, but I'm nervous about wine stains," he says.

All the furniture was designed by Mathers, with input from Massow. "I sketched the sofa on a piece of paper, knowing that I wanted three and that they should be long, wide and flat." Rectilinear wooden shelves echo the floor-to-ceiling cherrywood cupboards, behind which he hides masses of suits: "Unfortunately, I have to wear them, but I hate them." There are also hidden spaces for personal computers, in case he has to work at home. The only thing about the refit that isn't right is the bowl-like sink, which Massow finds too splashy. "Completely useless. It looks nice but doesn't work." And he has also taken a long time to remember which of the taps is hot and cold. But the big showers are more fun, and even have sideways jets.

In another nose-thumb to his less-is-more stylists, Massow has scattered the place with artworks. Dotted around are a handful of romantic Russian portraits from the early 20th century. In his bedroom, there is a print by Leon Kossoff of Christ Church, Spitalfields, Hawksmoor's masterpiece. One bathroom has a painting of a Sussex farmhouse by James Knight's father, and above the fireplace in the living room is a posthumously commissioned portrait of James by Sacha Newley, Joan Collins's son and a friend of Massow's. Another bathroom has a Horst portrait of Bette Davis that he bought on his second date with James.

After his bereavement, Massow was "absolutely useless" but now he is back entertaining again - part of the reason behind the large kitchen- cum-living room top floor. "If I thought about how I wanted to live, it would be in this room, because I love cooking while people are sitting around and chatting," says Massow. Soft light comes from an opaque skylight and there is a small outside terrace, overlooking mansion flats. The most unusual feature is the fire: "I call it cat-litter." hen turned on, flames waft eerily through small stone chips, like a tomb for an unknown soldier.

It is more important to Massow to have a place in the country than in London. He has three horses at his farm in Sussex - "I take my riding very seriously" - and is master of the local bloodhounds: the sort that chase humans rather than foxes. The hunt's logo was, "e hunt men for fun", which the committee decided to change in view of Massow's sexual orientation.

Sadly, he is too busy at present to enjoy his country seats, though he is becoming quite concerned about his Somerset house, which is in the process of being give a Grade One listing. "It has beautiful high ceilings and is like something out of the Mayor of Casterbridge," he says. "But I know I've got two years of waiting for English Heritage to muddle through." Clearly, he wishes he could do to the conservation world what he has done to the insurance business