Nor is this Adam, despite the evidence of his conservatively tailored suits and the affectation of gold pince-nez, an architectural throwback. He may be an excellent old-fashioned draughtsman and a noted scholar, but he also deploys computers and mobile phones, has a website, drives the sportier kind of Volvo, and - where other niche-market classicists tend to stick together - he likes to mix it with the modernists. "Architects," he likes to observe, "always have more things in common than they have differences." At the public inquiry into the Hampshire house proposal, he was supported by both Michael Manser, a veteran arch-modernist architect, and by Professor David Watkin, a noted Cambridge architectural historian of the traditionalist variety.

The house - for a wealthy local farming and landowning family, the Everetts, who live in an existing farmhouse nearby - is inevitably grand, with its stone-built main block housing the main living rooms and bedrooms, and a subservient more domestic brick-built wing for the children and nannies. There is also a separate but linked copper-domed tower - with the main bedroom on top and the estate management office beneath. What with all that and a garage block with servant' quarters over, swimming pool in a large conservatory, tennis court and so forth, it will cost at least £3m to build. But in investment terms it's a winner. Arable farmland is worth very little on its own: but landscaped as a 50-acre park with a big house on it near affluent Winchester, it will probably be worth nine or ten million, should its owners ever find themselves strapped for cash. Not that they anticipate this: Tim and Grace Everett, both still in their thirties, say they are building their home for life.

So it may be sumptuous in terms of accommodation, but in design it is, in contrast, rather restrained, scarcely ostentatious in its calm, orderly way. There is no looming power-colonnade, no monster pediment, no encrustation of ornament. You get plain pilasters, shallow roofs concealed behind balustrades, large areas of glass, and a little pediment, surmounting the central entrance bay, that is so understated as to be almost unnecessary. Adam sometimes designs by implication - the proportions of his buildings can suggest an underlying classical order rather than flaunting it. Such absence of detail, as with minute doses of alternative medicine, can be highly effective. The Hampshire house is not quite of that homeopathic variety, but it still possesses the slightly stripped, erased quality that you find, for instance, in the houses of the great mid 19th century Scottish classicist Alexander "Greek" Thomson, or the 20th century classical work of Sir Albert Richardson. Thomson's Glasgow buildings were startlingly advanced for their time.