Playing to the Galleries - Mayfair times

David Rosen takes out his wallet, unfolds a piece of paper from it and shows it to me. It`s a quote from the 1950s detective writer Raymond Chandler. It starts: "Down these mean streets a man must go who is not himself mean, who is neither tarnished nor afraid."

It took just 20 minutes at our first meeting to discover a mutual passion for Chandler's work. I'd shared the "mean streets" quote with Rosen and he had immediately suggested a "mean streets" stroll around Mayfair. It was nice to see he was carrying the quotation with him.

Rosen is senior partner of Pilcher Hershman, a surveying practices established way back in 1932. He joined as a boy in the role of trainee negotiator in the mid-1970s has never worked anywhere else, gradually working his way up to the top slot.

At the same time, he built himself a reputation as a man interested in art, architecture, space and light; a man with a knack for finding New-York-style spaces for his growing collection of art dealer clients. In the process, he was made an honary fellow of the Royal Institution of British Architects - an award that is not given lightly.

It was Rosen who found Hauser & Wirth its stunning 12,500 sq ft gallery at 23 Savile Row, just a short walk from his own office in a former tailor`s shop. He also spotted the potential of an old garage in Britannia Street, Kings Cross, where Larry Gagosian now has a gallery. And he helped get Saatchi into its iconicand vast Chelsea gallery in a former military HQ at Duke of York Square.

Rosen is startlingly well connected in the world of art and architecture and as we walk between galleries - Hauser & Wirth, Timothy Taylor, Sadie Coles, James Hyman - he greets and is greeted by many people, including at one point the art director of a leading fashion magazine. But then he' s a friend of Neville Brody, the leading graphic artist and typographer who designed The Face and Area and, incidentally, Pilcher Hershman's logo and letting boards.

"Invariably with galleries, particularly contemporary galleries, it's about volume" Rosen says. "They're not worried about rent per sq foot, it's all about rent per annum and in a sense it's all about cubic capacity. From a landlords point of view it's all about rent per sq foot, but nobody measures cubic capacity - and that's for free, that space. When you think of the scale of the work that's being sold, it`s sitting in that cupic capacity."

Indeed, when Rosen was commissioned by Larry Gagosian to find new gallery space, Gagosian's brief was that it needed to be able to house a Richard Serra sculpture. That takes a lot of cubic capacity. And when we drop into Hauser & Wirth, the centrepiece is Louise Bourgeoise's huge spider sculpture, which I`d first seen at the Tate Modern.

After he was appointed by Iwan Wirth to find Mayfair space on a New York scale, Rosen trawled the streets looking for "interesting opportunities."

"I was walking back up Savile Row one day and we passed the site of the old English Heritage building, which was still under consideration," he says. "I was actually with Iwan, and I said, 'Come with me and lets just see if we can get in, because this looks really interesting'. Because the street is sloping on Savile Row, the space from the street doesn`t read as high as it does once you get inside. We walked inside and it was the north gallery we went into, and he just said, 'This is perfect'"

Art dealer Simon Lewis once described Rosen as "more of a detective than an estate agent" because of his ability to see the potential in unlikely buildings.

It`s a description that Rosen the Chandler fan is probably quite happy with.

The Simon Lee Gallery, incidentally, is now in Victoria - in a former Royal Mail sorting office hunted down by Rosen.