Property: In the hands of modern masters: Collett and Champion houses cost a large fortune, but, says Anne Spackman, they are splendid works of art

The Old Rectory at 56 Old Church Street, just off the King's Road in Chelsea, is set to be the most talked-about property of the year. The size of a country house, with two acres of garden in the centre of London, its main claim to fame is its price tag, a staggering pounds 25m.

You may remember the last house that carried such a burden of expectation. It was the Towers in The Bishop's Avenue, Hampstead, which finally sold for a paltry pounds 10m at the end of 1992.

The two houses could hardly be more different. The Towers became famous as an icon of naffness, inspiring the wickedly appropriate term 'Kentucky Fried Georgian'. The Old Rectory, on the other hand, is the most prestigious work yet of the design partnership of the moment: Collett and Champion.

Anthony Collett and David Champion's clients are graduates of the Conran Shop school of taste - wealthy international people who admire the new as much as the old. Collett and Champion houses have a strong, contemporary feel, but it is achieved through classical form and the use of materials such as wood and marble, rather than the uncompromising steel and glass that have made so much modern design harsh and alien.

They made their name doing private houses and offices in Japan, the United States and Europe. One of their clients in London is Conrad Black, the international newspaper magnate and owner of the Daily Telegraph.

The Old Rectory is the result of their association with a Japanese businessman, Norikazu Nemoto, who has entrusted millions of pounds to their artistic hands. Though all three are directors of Toyoko Metropolitan Company (TMC), which developed The Old Rectory, Mr Nemoto's role is that of a patron, providing funds to support Collett and Champion's work.

The trio's most recent project, now for sale through Knight Frank & Rutley, is 47 Rutland Gate, a grand house near Harrod's. From the outside it looks like all the other smart white terraces, and even inside the first impression is of familiarity. What makes this house different from its neighbours is its space, practicality and, most important, detailing.

Most London houses, however expensive, suffer from the same problems. They contain a number of rooms designed for life in a previous age, often served by ancient wiring and plumbing. They are either still afflicted by a previous generation's woodchip, or have been expensively chintzed and Smallboned during the Eighties. Also, they have no garages.

The Rutland Gate house has a garage, wine cellar, laundry, and staff accommodation with a separate entrance on the lower ground floor. Even that accommodation has been thoughtfully done. 'We've seen too many shoe boxes for Filipinos,' says Mr Champion, dryly.

The two main living floors (accessed by a concealed lift as well as stairs) contain three vast reception rooms, a kitchen made of oak, and a library panelled in cherry wood - all of which can be opened up to provide acres of entertainment space. The lavatories and bathrooms, as in all their houses, are stunning, with cupboards concealed in curves of rich woods such as maple, and solid wood duck- boarding in the showers.

Lorna Vestey, of Knight Frank & Rutley, who is handling 47 Rutland Gate, says attention to detail and quality of finish make Collett and Champion's houses special. 'They are perfectionists,' she says. 'I've seen Tony Collett take down a loo ceiling because it was a fraction of a millimetre out of true.'

Like the Old Rectory, this is a speculative build for sale, rather than a job for a private client. It went on the market in October with a price of pounds 4.95m, and is said to be attracting strong interest from an American and an Indian buyer.

The international appeal is hardly surprising. Collett and Champion met in their native South Africa, and their work has a hint of African ethnicity about it. Together with their Japanese backer, they understand the common requirements of what used to be quaintly called the 'jet set': large entertaining spaces, parking, lots of bathrooms with good showers, and, where physically possible, swimming pools and exercise rooms. (The Old Rectory has a pool lined in black marble, with an underwater window through to the gym.)

TMC could have developed property anywhere in the world, but Nemoto settled for London. 'Our work is drawn on classical lines,' Anthony Collett says, 'and that is so right for a city like London.'

Though they take their work seriously, Collett and Champion are not unapproachable aesthetes. Instead, they are an exotic mixture of style, humour and warmth, a kind of low-key double act.

Next door to the Old Rectory they are developing 58 Church Street, a long, single-storey house built around a series of four courtyards. Its front door, a huge copper cylinder set in a square frame, is a classic Collett and Champion feature.

They bought the house in a dilapidated state in 1990 for pounds 8m, to protect their investment in the Old Rectory. Though they sit side by side, the two houses are separate and different. Number 56 sits proudly behind a sweeping gravel drive; number 58 is on an odd- shaped site and reveals only a fraction of its size to the street.

The Old Rectory is under wraps in preparation for its launch in the spring. It has been three years in the making, during which the two designers have battled with English Heritage over the tiniest details, down to the choice of nails for the floorboards.

Now English Heritage - like everyone else who has sneaked a look at the house - is happy. All TMC needs is a buyer.

Few of the people in the world with pounds 25m to spend on a house are from outside the Middle East. But the Old Rectory is unlikely to appeal there. Most observers expect a European or American buyer to move in to England's smartest new address. Are the design team nervous about this last stage of the project?

'We certainly are,' Mr Champion says wryly.

(Photograph omitted)