Bohemian rhapsody.

Poised like a light-filled eyrie above central London, this modern urban loft is dramatically colonised by a series of immaculately crafted insertions.

In spite of their romantic associations - with New York lofts, Bohemia, cheapness, youth and so on - warehouse spaces are often amorphous, expensive, draughty and in inimical surroundings, requiring imagination and money to make them habitable, and a car to take you away from the area in the evening.

In making a flat for one person out of an empty half-converted shell at the top of a London warehouse, Brookes Stacey Randall Fursdon has demonstrated considerable inventive powers as well as poetic sensibilities. The client is Chris Lowe (of the pop group Pet Shop Boys) who having trained as an architect has an eye for space and detail. He loved the views across London and of the skies, but required a measure of privacy and security.

The space itself is not particularly large on plan, but it is airy and glazed on two sides. The roof of the existing shell is a half arch curving over a long rectangle, flanked by a smaller room and barely separated from a roof terrace by a glazed wall. A spiral staircase on the terrace leads to an upper one on the north side of the building. In designing a civilised dwelling, the architects' main concern was to enhance the warehouse's spatial qualities while at the same time providing the usual domestic facilities.

The single volume was retained, with space only minimally interrupted at the entrance by the insertion of two full-height curving walls. The device has a dual function. One has to do with the drama of emerging from a dimly lit passage into an expanse of light-filled space; but more practically, the passage becomes a fire lobby in an emergency. When the alarm goes off, a full-height fire door swings across the passage.

With the living area naturally overlooking the terrace, the other end near the entrance became the kitchen/dining area. The smaller room was divided into a light-filled bathroom and storage area, and a sleeping gallery was built at mezzanine level. Cantilevered out from the base of the arch towards the upper terrace, it was connected to it by an elegant glass bridge.

The surprise and invention present in the planning and detailing of this flat is a constant source of delight - and one of wonder at the amount of time that is incorporated in each detail, that must have been spent simply on research.

The inflexibility inherent in a single space has been solved in a particularly ingenious way - the result of a happy collaboration between the architect, engineer and contractor. Three large pods built into the storage room between the kitchen and living area slide smoothly out of the wall on cantilevered runners, in principle similar to those of filing cabinets and eliminating the need for tracks in the floor. One contains kitchen and dining equipment - cooking utensils, crockery, glasses - and stores; another has hanging and shelf space for clothes and bedding; the third provides room for hi-fi equipment, record storage and mixing deck. In an instant therefore, the kitchen can be screened off, the main room can become a music and recording studio, or a dressing room. The pods are completely interchangeable: the storage boxes, shelves, rails and work surfaces have common fixings so that as the client's needs change, the elements can be unbolted, replaced or changed.

There is evidence of other interdisciplinary collaboration. The staircase to the gallery has glass treads and risers and has been designed to be as light and transparent as possible. The glass has been used structurally to form a folded plate in one direction and a truss in the other; no other structure is needed to hold the treads in space.

Above the sleeping gallery, a double-glazed rooflight inset into the curve of the roof opens on hydraulic arms. You can lie in bed under the stars and see St Paul's Cathedral; but the rooflight is also the door to the upper terrace at the end of the curved glass bridge. By such means, the terrace outside becomes an extension of the interior, an outer room illuminated at night by a specially designed standard lamp, a disc of reflected glowing light like the moon.

Light, dark and privacy are constant themes in the design. Irregular hours are part of life in the music industry, and the client needed to be able to shut out light during the day in order to sleep. The rooflight and glazed walls can be screened by automatically pivoting aluminium louvres; and the end glazed wall rendered private by rows of tall swivelling glass fins faced with a thin veneer of birch wood. The effect of this is magical, for much as thin sheets of alabaster were once used like shoji screens to transmit light, the sheets of birch are translucent and shed gold light over the interior. Kitchen and dining areas are screened from public view by panes of acid-etched glass, held from behind by a slim stainless-steel support so that the translucent panes appear to float.

Other touches of delight are present: in the immaculate detailing of a kitchen counter in laminated beech or the slender oven hood, specially designed to eliminate the usual monstrosity; or finally, in the shower, where a fibre-optic light inserted into the showerhead shines through the drops of water in celebration of invention, and of water.