Secret in the City

A converted warehouse offers privacy in the heart of London's Square Mile. Nicole Swengley discovers a hidden treasure

Middle Street, EC1, is one of those narrow lanes where it's easy to conjure the ghosts of medieval London. It lies behind the cobbled streets of Bartholomew Close and Cloth Fair and is barely wide enough for a car to squeeze through. The Museum of London and the Barbican are just a stone's throw away.

Stroll past the street's eastern end and you barely notice the last building. Grey painted walls and frosted glass windows give way to an upper storey of glazed white brickwork. Behind the simple façade, however, is an imaginative conversion of a former warehouse, in which an industrial look has been tamed into a sleekly good-looking and very private domestic interior.

For 10 years, architect Ken Mackay had been searching for a City property to convert into a home. Sitting in a pub one day, Mackay spotted a For Sale sign being erected on the office block opposite; he bought it the next day. Planners at the Corporation of London were intrigued - most of its 3,500 residents live in the Barbican, and there are only 300 homes outside the complex - and gave the project their blessing.

The five-storey freehold property offers 4,243 sq ft of living space - roughly double that of a conventional townhouse. One reason is that the unaltered basement and ground floor, which have their own entrance, are primed for development into a home office, gym or private cinema. It could also be closed off for use as a nanny-flat, although the property is probably better-suited to a couple of City high-fliers - people who travel a lot but enjoy entertaining when at home - than a family with very young children. Teenagers or twentysomethings who haven't yet left home, however, might appreciate the potential for separate accommodation.

Perched at the top of the building is a master bedroom with security-glass sliding doors opening on to a roof terrace. It's a light, bright nook - a private eyrie in the City. A wall of Japanese frosted-glass blocks divides the bedroom from an en suite bathroom that wouldn't look out of place in a luxury hotel.

Descend the self-supporting, winding oak staircase and you reach a landing with a utility room and cloakroom, whose stainless-steel lavatory and basin are the epitome of "prison chic". As you enter the huge living room - about 30ft long by 20ft wide - your eye is immediately drawn to the far end, where floor-to-ceiling security-glass sliding doors frame the distant Barbican towers and open on to a slim balcony that overlooks an outdoor walled courtyard on the level below.

The overall look is reminiscent of an industrial loft, yet softer and more homely, and Ken Mackay's love of raw construction materials are much in evidence. A wall of floor-to-ceiling frosted glass blocks runs along one side of the room, screening the interior from surrounding office blocks.

Mackay explains that the light-reflective glass is particularly well-suited to the room's northern side. A couple of clear glass windows offer edited views of the outside world and some ventilation. The opposite wall, like the floor, is pale limestone and punctuated with walnut cupboards and a plasma-screen television. Look up at the ceiling and a zinc sheet, crinkled like folded paper, adds an urban allure.

There are surprises around every corner. The staircase winds around a box-like chainmail structure whose internal lighting makes the material sparkle at night. Full-height black American walnut doors admit you to the kitchen-cum-living room. Again, your eye is drawn to the floor-to-ceiling security-glass sliding doors at the far end of this vast room. Beyond, the decked courtyard is surrounded by high walls in which a sash window is retained in a portion of original wall while a fixed pane frames a tree across the street.

Inside, the crinkly zinc ceiling and frosted glass-block wall echo the room upstairs. The floor, however, is blonde maple, while a kitchen island and run of wall units are made of seamless white Corian. The built-in ceramic hob and handle-free drawers and cupboards enhance its sleek good looks. Above the work surface a long, slim run of storage units are concealed by split surfaces that concertina to each side when opened.

Descend again, passing open brickwork from an original wall, and you reach a corridor, off which are two tiny bedrooms and a bathroom. At the far end is another bedroom, whose en suite bathroom has a large walk-in limestone-lined shower. Like the master bedroom's en suite, it is kitted out with a pair of circular white basins on a limestone vanity unit.

Several examples of intelligent technology make it easier to live in this multi-storey block without a lift. A large dumb-waiter serves all floors while the Lutron wiring system can be operated from each room to control lighting, security and entertainment. More impressive than the electronic gadgetry, however, is the use of construction materials not usually on show in a residential property. It's as if the physical elements of the building are artworks themselves.

The underneath of the staircase, visible from several levels, has been joined and plugged with as much care as the surface. The zinc ceilings add gritty glamour. The frosted glass walls look visually attractive while filtering day-light and offering privacy. Then there are the occasional reminders of how the building once looked - an original sash window here, a tranche of brickwork there. It's hard to know whether the house is a domestic slant on an industrial building or a commercial take on residential living. It's up to city-lovers with £2 million to decide.

15 Middle Street, EC1 is available freehold, subject to contract, through Hurford Salvi Carr (020-7250 1012, www.hurford-salvi-carr.co.uk)

Mak Architects (020-7600 5151, www.makarchitects.co.uk)