The top of the market has been quick to step into the breach. Northacre, the developer of the hospital, has already seen the value of major excavation work at Observatory Gardens. Certainly many buyers who have abandoned west London for Docklands cite parking facilities as a real incentive.
In many quiet residential roads, parking problems have provoked open warfare. An armoury of wooden planks, dustbins and traffic cones are deployed as soon as a car noses out of its usual spot; number plates are jotted down in the case of long stays and notes are left asking the drivers to move on. Parking is not just an issue in central London, where residents have long been resigned to restrictions and permits, but increasingly on the inner-city fringes where people still take parking for granted even though affluence and gentrification now mean at least two cars to each household.
More buyers than ever are putting ease of parking on their list of priorities, while vendors realise how valuable it is as a selling-point. Lucinda Comyn, who lives in a quiet Wandsworth street, finds the constant anxiety about spaces stressful. Her predicament is becoming common in all cities: a nearby permit zone has created a problem where there was none. "You have to be able to park near your house if you have 15 bags of shopping and children. You see mothers cruising around desperate for a spot. I have a two-year-old child and I am so worried about never getting my parking spot back, I hardly ever use my car. It's ridiculous, and I suppose we could do without two cars, but there is always the feeling that there might be an emergency."
Agents suggest that buyers investigate the opportunities for parking. Rather in the way that roads without humps see a disproportionate amount of traffic (another useful consideration), what seems like an oasis of free parking can quickly turn into a nightmare akin to living in a long- stay car park for commuters. Lucy Woolley, editor of Living South, who has campaigned for better parking management, believes that residents with at least two large cars will eventually have to bear the cost. "It is ludicrous that there are more four-wheel-drive vehicles in London than in the whole of Wales."
Given that houses with garages are rare in cities, properties in popular areas where the front garden has been converted to a parking area carry a premium, as much as pounds 50,000 in certain places. "Some buyers will sacrifice an extra bedroom or a garden if there is a garage," says Matthew Kaye, of Chesterfield. "They can also be very particular about which permit area a property lies in. Kensington and Chelsea is more desirable than Westminster."
In cities such as Bath, which has the additional parking headache of being a tourist attraction, it will cost about pounds 20,000 to buy a garage in the prime Georgian parts. "The increase in the number of house conversions to flats has put a tremendous squeeze on unrestricted parking, says Paddy Stewart-Morgan, of Cluttons. "A nice house within walking distance of the station sells for between pounds 300,000 and pounds 400,000, and has risen in price over the past six months."
In Oxford, which similarly plays host to hordes of tourists, the council uses stringent planning controls to restrict traffic. Cluttons finds that a four-bedroom town house will sell for about pounds 25,000 more with off-street parking, and this can add up to pounds 15,000 to a pounds 100,000 flat.
It is no wonder that garages themselves can be a good investment, and particularly where they do much to enhance the value of a property. Douglas & Gordon had a home for sale on Chelsea Embankment that would not shift. The only interested buyers were insisting on having somewhere to park. When a garage close by went on the market for pounds 75,000 they bought it, and within a matter of weeks the sale was agreed on the house.
Andy Buchanan, of John D Wood's Chelsea office, has seen the prices of garages, which have generally stayed pretty steady, go for staggering prices where it becomes part of a package. "Spending pounds 100,000 on a garage if you have a pounds 2.5m house makes the property even more valuable. Families who buy pounds 800,000-to-pounds 900,000 homes in the World's End area would regard pounds 50,000 for a garage at the end of their street as a bargain."
But before anyone imagines that all garages in London have money-making potential, Mr Buchanan warns that many are poky, with difficult access. There has to be room for a good-sized car, not just a motorbike and a few boxes. "Their entrances are always being blocked by drivers who know they cannot be clamped for parking there, only towed away."