The extension occupies the entire rear garden, thus ‘urbanising’ & ‘Inhabiting’ the site. The enclosed space wraps around the courtyard and is defined by a continuous band of full-height sliding glazing. These windows can be fully opened to create a single sweep of space from one end of the house to the other, which discourages conventional distinctions between the indoor and outdoor. The palette of material is restrained and monochrome. It has white fair-faced concrete block walls, stack bonded with white mortar, white rubber floors internally and white acid-etched concrete paving slabs externally, and mirrored worktops and roof. The mirrored roof - surely a first - has a delightful ambiguous quality, hovering at the boundary between art and architecture. In sunlight, it lies flat and blue, suggesting the glistening surface of a California pool; at night, or under an overcast sky, it is more mercurial, evoking the unfathomable depths of another memorable London piece - Richard Wilsons' oil installation (20:50) at the Saatchi Gallery. Extract from the Architect’s Journal, by David Jenkins Photo copyright Sue Barr