In the case of Peter Clifford, those doors reveal a large studio where he teaches Tai Chi Chuan, empty except for two antique Chinese beds and, this week, his two-year-old son, trying out a birthday bicycle.
Most Londoners have at some time stumbled across a mews they never knew existed. Hidden behind grand buildings and glimpsed from traffic-clogged streets they offer an irresistible but central retreat from city life.
Peter Clifford was smitten while living in a west-London flat that overlooked a mews. It had a romantic, other-worldly appeal - "the cobblestones glistened in the rain," he recalls. Now he is the owner of not one, but two mews houses, commuting from the large to the small.
Outside his family home in Astwood Mews, south-west London, two stone statues from an Indonesian temple stand guard. Above the studio - previously used as a cinema by Nicolas Roeg, the film director - the living- and dining-room soar to the full height of the house. There are few types of property better suited to the current trend for altering dramatically an interior while retaining the original facade. Old stables are not packed with features of architectural merit and designers have virtually a free hand, providing the house is not leasehold.
"You never know what a house will look like inside, but the mews itself has the feeling of old England," says Peter Clifford. "It's a small, friendly community as close to a village as you can get in the heart of a city. One neighbour gave us all a tub of flowers to put outside and another holds parties for everyone. But there are also working garages opposite and I really enjoy the contrast between the bustle and the extreme quiet."
The original working purpose of the mews can be lost on those keener on its gentrification than its history. Antoine Lurot, who started the London Mews Company more than 25 years ago, has few kind words for those who would like to see the garages disappear altogether. "All they want to do is shut everyone else out and increase the value of their property. Some people who object at first after a while begin to say how wonderful the garages are because they take in their parcels and sort out their cars."
He has some sympathy, though, with those who have privatised their mews, taking over the upkeep of the road. "If people block you in with their cars, roll out of a wine bar noisily and pee on your wall every night it is not really surprising that you might want to keep them at arm's length."
Lurot has seen the mews through its many changes in status. The pop stars who haunted them in the Sixties and Seventies are now more likely to live in the grand house than in the grooms' quarters, however pretty. "They are still not family homes. They suit just about everyone but the couple with 2.4 children," he says. "The greatest mistake people make is trying to squash in too many bedrooms."
Good design is the key, he adds. Nothing too fussy and put the staircases in a dark corner. He has over the years walked into some memorable schemes. "In one little house the garage doubled as a dining-room. The table and chairs were hauled up to the ceiling on a pulley when they were not being used. The car was then driven into the space and parked on top of a steel tray so that oil didn't dribble on to the carpet.
"In another house, you walked through the double doors into the sitting- room, pressed a button and the whole room rose revealing a lift in which you parked your car and then dispatched to the basement. The sitting- room was then lowered to the ground floor again."
Such extravagant schemes may be rare, but they dash any notion of the mews house being small, dark and twee. Antoine Lurot says the average is around 1,200 sq feet. There are, of course, those of around 600 to 800 sq feet - perfect pied-a-terre property.
On the Grosvenor Estate, FPD Savills has an exceptional mews house of 6,000 sq feet on the market. The pounds 4.5m house has an 80ft frontage, a conservatory, a 97-year lease and, most unusually, a garden. On the original site of the Tattershall horse fair, it was part of the redevelopment of Grosvenor Crescent.
Two years ago the last horses left the mews with the tenants. Mews with a mix of horse and house are dwindling and likely to be found only north of the park. Off Belgrave Square, in Groom Place, Savills has a more typical small mews house in a cobbled street for sale at pounds 725,000, freehold, with garage and parking.
Traditionally placed at the bottom of the rich man's garden, mews houses do not have their own patches of grass, and in case the stable staff were tempted to snoop, the houses often have no windows at the back. The many oases of green that can be seen on the roofs of mews houses are more suitable for sipping a glass of wine than kicking around a ball, and it is the lack of garden that has forced Peter Clifford to think beyond his mews, or at least one of them. "It is a wrench, but we need more space as a family. I will always keep the smaller mews though. It is a wonderful place to work."
Astwood Mews is on the market for pounds 675,000 freehold with The London Mews Company (0171-402 3275). FPD Savills, Sloane Street (0171-730 0822)Reuse content