Off, then, to Wiltshire, where few people are aware of the existence of the private Roche Court sculpture park, a few miles outside Salisbury. Roche Court is a house and farm that also acts as an art dealership - it does a trade particularly in Barbara Hepworths - but which is also throws open its hundreds of acres, free, to the public. Its energetic patronne, Madeleine Bessborough, decided she needed a small enclosed gallery to display more intimate pieces and sculpture-related drawings. She called in the rather chic London architects Munkenbeck and Marshall - notably Steve Marshall.

A wall ran between the house and a small, detached orangery that was already used for low-key displays. Marshall rapidly sketched out a narrow gallery set against this wall to link the two existing buildings. He envisaged an uptilted, seemingly floating roof and an all-glass wall taking in the lawns and trees of the surrounding gardens, dotted with sculpture. And this sketch - the first idea - is pretty much what has been built.

There was no need of Lottery funds here, since Roche Court survives very well on its own resources, but all the same the New Art Centre, as it is called, is a small and low-cost gallery. It was assembled by local builders but is anything but provincial - the workmanship is distinctly higher than you'll usually find in the capital.

So many buildings that look good in photographs disappoint when you see the real thing. Not so here, where Marshall has contrived something entirely modern and transparent which is completely at ease in its traditional country-house setting. The uptilted pale aluminium roof is held clear of the wall at the back by a slot of top-glazing to provide even daylight. The glass facade is divided into three sections by two full-height narrow cedar doors, which open the space up to the outside world in fine weather. Cleverly, the pintles concealed in the thickness of these doors are also the very slender columns holding up the roof - which thus has no visible means of support.