THERE is no bigger box of tricks in London. Better still, the tricks are both ancient and modern. The house, though built for the Dowager Duchess of Northumberland in 1770 on the edge of the Percy family’s glorious Syon Park estate on the Thames, is more familiar in its second incarnation as “Crowther of Syon Lodge”.

Tom, Bert and Derek Crowther were among Britain’s most famous, and occasionally infamous, dealers in antiques, garden statuary, marble fireplaces and entire period rooms, which they shipped both ways across the Atlantic; Vanderbilt ballrooms from New York would appear in their brochures. Syon Lodge looks the perfect grand Georgian teacaddy house but, in fact, much of the interior came from other grand houses. “My great-grandad, Bert, bought it derelict from the 8th Duke in 1928,” says Paul Crowther, who is now selling it for £6.75 million.

Paul bought the house in 2005, two years after his father, Derek, closed the family business. Paul was determined that the one-acre garden should not go the way of the next-door lot and be packed full with Georgian-style townhouses that look as if they are cardboard cutouts from Toy-town. “My father said: ‘Put up or shut up. If you want it, pay what the developer will pay’.” After the firm closed, says Paul, all its records, telling a story of a vanished world of English and Scottish town and country houses, went on the skip.

His girlfriend is Polish and for two years skilled Polish craftsmen have transformed the house from showroom and rundown offices into the smartest gizmo-packed residence in London. “It took two men 18 months just to relay the York paving in the garden,” Paul tells me as we stroll along the perimeter walk. “Some of the slabs are this thick,” he says, making a ten-inch handspread. “Each slab took four men to lift,” he adds. When I admire the neatly planted squares of vegetables, he says: “Our Polish builders grew their own veg, and caught fish in the lake.” This is evidently the lake just across the garden wall in Syon Park.

“Everyone said: ‘With a big garden like this why don’t you build a swimming pool and a gym?’ ” Instead there’s a cascade pouring down a giant rockery, two fountains, a salvaged Venetian loggia made of the same glorious pinky marble as the Doge’s Palace and a Strawberry Hill Gothick summerhouse that his daughter uses for yoga and meditation. Grand steps lead to a front door surmounted by a fanlight as exquisite as any in Georgian Dublin. Inside there is the finest carved medieval stone fireplace I have ever seen in England, complete with a high relief carving of St George slaying the Dragon. There’s also a wealth of faux Elizabethan ceiling plasterwork with Tudor roses and thistles. In the hayloft Paul has made a sleek modern flat. But that is nothing to what awaits in the main house. Here high-tech rules. In the drinks room a cupboard opens to reveal music systems for every room and the workings of a power-assisted satellite dish on the roof.

In each room there is a panel allowing you a choice of world radio, or you can play your favourite, preinstalled music. Music for an allnight party or for a children’s do is instantly available – or you could listen out for baby in another room or announce that dinner is ready.

The mosaic-floored, walk-in showers are large enough not to require doors. Shower heads the size of frying pans give a downpour of tropical intensity. There’s underfloor heating and heated chrome ladder tower rails. The master bathroom has a TV with surround-sound in its own glass-fronted box – just as Charlie Chaplin had in his 1957 film A King in New York (complete with windscreen wiper).

The cinema room also comes with full surround sound. “I heard of one Premier League fanatic who paid £50,000 just for a projector but that’s going too far,” Paul says. The LED lights on the skirting are another trick, giving a low glow so children do not feel left in darkness. The CCTV cameras allow the house’s owner to keep an eye on it from a laptop anywhere in the world.

If you buy Syon Lodge, one thing is certain: you’ll spend a lot of time being the tour guide.

Take a tour around the finest country houses for sale in Britain at: timesonline.co.uk/marcusbinney

FACTFILE

WHAT YOU GET: Large townhouse with nine bedrooms, one-acre garden and separate flat in stable wing; electronic wrought-iron gates; in all 9,715 sq ft.

WHERE IT IS: London Road, Isleworth. Eight miles to Hyde Park Corner.

PRICE: £6.75 million through Featherstone Leigh, 020-8940 1575

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