A Tardis-like Holland Park flat by Spencer & Wedekind

As Nicholas Spencer takes me on a tour of a project he has recently completed in Holland Park, I marvel at how a highly skilled interior designer can bequeath a Tardis-like quality upon an interior that, on first impression, has just a modest amount of space. Three bedrooms, two of which have en suite bathrooms, a large kitchen and dining room, and a sitting room with enough space for a family of five all on the top floor of a house? Surely the laws of physics have been broken.

The flat is at the top of a substantial Regency house in a part of Holland Park where some of its unconverted counterparts are home to minor embassies and consulates. At 140 square metres, it is hardly a shoebox. That said, Nicholas and his wife Sophie, who make up the interior architecture practice Spencer & Wedekind, have created an interior that is far more than the sum of its square metres.

It was a project that required an imaginative approach to problems, the confidence to try something new and a handful of tricks that deceive the eye in the most pleasing of ways. However, Nicholas soon learnt it was also a project that required the patience of a saint. 'When we started stripping it all back, we'd see a little bit of mildew here or there, some yellowing on the walls or wallpaper starting to peel off, so we knew there was something wrong.'

What no one suspected was that the entire roof would need replacing with one that would require reinforcing from below, and that the ceiling would also need to be removed and replaced - with faithfully reproduced cornicing, due to the building's Grade-II-listed status. Interior work was put on hold for seven months. 'What was meant to be a project with some restructuring of the layout and decoration turned into a major build,' Nicholas recalls.

Good fortune came by way of the clients, who sound like an interior designer's dream come true. Both work in the music business, with jobs that require a relentless international travel schedule. It meant that they had little time to um and ah over decisions and could let Nicholas continue to drive the project forward. Although not extravagant, the budget was enough to allow the appropriate attention to detail. The owners' familiarity with some of Nicholas's previous projects also meant they gave him virtual carte blanche to fulfil a minimal brief.

Today, the flat is a perfectly ordered space, with a small hall at the entrance dividing the bedrooms from the living areas, which include the east-facing sitting room at the front and the kitchen and dining area at the back. Dividing these two spaces is a set of glazed pocket doors, which allows natural light to always fill the middle of the rather deep building. Cleverly, the doors have been positioned to hide the working area of the kitchen, saving the owners from staring at pots to be washed while they relax in the sitting room. The wall between the two rooms has been deepened around the doors to make space for storage, which also creates the effect of a mini-hall.

Storage, in fact, is one of the underlying features of this flat. One point that came out of the brief was the owners' aversion to clutter, which led to the siting of the oven within the white, streamlined kitchen units. In the sitting room, a hip-height wall of built-in cupboards, punctuated by upholstered nooks on which to perch under the windows, contains a drinks cabinet, a hinged unit that transforms into a laptop-size desk and additional storage. Their modest height, and the white walls that are largely unburdened by artwork, prevent a room with relatively low ceilings from feeling too closed in. Perhaps because of the generous amount of joinery - both evident and discreet - the flat has a handsome quality.