The first man in space: Derelict brick hulks are turned into fashionable spaces under David Rosen's hand, says Anne Spackman

David Rosen is the property world's version of a talent scout. He walks the streets of London, often in the unlikeliest places, looking for underrated buildings that can be transformed into fashionable offices and homes.

Today we are in King's Cross. Even the most lyrical estate agent would be reluctant to describe the area, now notorious for its prostitution and drug-dealing, as a desirable residential site.

At 11am, York Way, the wide, one-way route up the east side of King's Cross station, is dusty and noisy. Despite the summer sunshine, it appears a hostile place.

Turning into Wharfdale Road, the derelict industrial buildings give way to terraces of two-storey, flat-fronted houses, the kind that in Kensington are now selling for pounds 400,000. But these are not what we have come to see.

Our interest is in the industrial brick hulks on the other side of the road. Up close, their imposing looks are transformed. The brick has been blasted clean, the warehouse windows have new battleship-grey frames, and the iron gantries are shining and black.

Behind a large, iron gate is a courtyard of modern apartments owned by the kinds of people frequently attracted to David Rosen's developments: photographers, designers, media people and architects.

At Gatti's Wharf, the first phase of a development known as King's Cross Marina, a dozen brightly painted canal boats are moored on Battlebridge Basin, a large area of water that dominates the scene. The London Canal Museum is housed in an old warehouse next door.

Across the water are the former offices of design consultants Fitch, in a building that served as an advertisement for their work. Next door is an architectural practice and an advertising agency. On the main stretch of the Grand Union Canal, at the end of the basin, is Regent's Wharf, another set of transformed buildings. These are home to, among others, the Wolff Olins design practice, which created the British Telecom logo.

All these buildings were once bottling plants or ice-storage factories. Their shapes and structures have barely changed from Victorian times. Their names are also, by and large, original.

Details such as these give the place the cachet of authenticity that new blocks of flats are unable to compete with. Places with history are much easier to sell.

That is one reason why Mr Rosen came here. Old industrial buildings are perfectly suited to the kinds of contemporary homes and offices which his estate agency business, Pilcher Hershman, prefers to sell. They have high ceilings, lots of space and light, and the appeal of authenticity.

Another factor that drew him to the area was the canal basin. This must be the closest stretch of habitable water to central London, apart from the Thames - and prices there would be a little steep for his clients.

A third appealing factor is the area's transport links. Nearby are five Tube lines, several bus routes, and, from the marina development, a short cut directly to the platform of the mainline station. London University and Regent's Park are within walking distance, Oxford Circus and Covent Garden not far away.

The process of transformation began with a walk like ours. When Mr Rosen or a colleague spot a good building, the company offers it to a sympathetic developer, such as Estates and General or London Buildings. The developer pays Mr Rosen's company a fee for having found the property and then employs an architect as part of the redevelopment. Pilcher Hershman then returns to sell the property.

The people this kind of residential space is pitched at are generally second-time buyers, reasonably young and predominantly childless. They are not as conventional or wealthy as their peer group in west London, who are served by more conservative agents selling traditional London properties.

The potential buyers tend to congregate in the 'black leather jacket' regions of London, such as Camden or Islington, where older agents are still loath to tread. Such buyers do not mind if an area has a few rough edges.

One reason developments such as the marina have survived the recession is because the sales people involved share the same tastes as their potential customers. In the same way that Sixties entrepreneurs found a ready market among their peers for rock music and fashion, so this group benefits from a common passion for good design.

At the corner of Battlebridge Basin is a reminder of the area's past. Albert Dock is a tall, narrow brick block sitting on an area of scrubby wasteland. The builders are converting each floor into an apartment of more than 2,000 sq ft with views from the top floors in every direction across London. Prices start at pounds 200,000 for a loft- style shell.

We walk back along York Way to a more recent discovery, a vast Thirties block, whose name is still unknown. London Buildings has just bought it, via Mr Rosen. The old delivery bay with a glass roof should be a double-height reception area in a few years' time, if all goes according to plan.

Farther down the road, set behind a car-cleaning business, is the next building Mr Rosen has his eye on. When we set out at 11am, it looked to me like an old railway yard. Now, two hours later, I can see its potential as a series of loft- style apartments.