Carl Fronda, of Tara swimming pools, an installation and maintenance company, disagrees: "Get in a helicopter and fly over London; you'll be surprised. There are more swimming pools here than California which is six times the size."
Tara is based in Lewisham and Carl regularly serves customers from suburban areas, alongside clients from places where it is hard to imagine private pools, including Blackheath, Lee, and even Catford.
So who is your average swimming pool owner? "It can be anyone, even in what you might call working class areas. They've got money, they don't want to move, so they add an extension and build a pool."
But how much money do you need? Around pounds 24,000 buys a concrete mosaic- tiled pool which is 16ft wide and 32ft long with a depth of up to 6.6ft. A pool with liner is around half that, but will eventually need replacing. Carl begins by explaining boiler sizes: "A 125,000 BTU heats a pool in three days but a 400,000 one takes two hours. Then there's your pump. I could talk about pools all day." Clearly a pool is not just about swimming. Installation requires precision planning if you wish to avoid hours of slow hoovering because of an inadequate pump.
Pools are de rigeur for those urbanites who can choose from the proliferation of London's latest developments. An apartment from pounds 295,000 or townhouse from pounds 530,000 buys access to a 68ft pool at Berkeley Homes' Harrods Village in Barnes. Islington's Angel on the Green development features a three- bedroom penthouse with a pool, for a cool pounds 1,000,000.
But there are established London buildings where residents have always enjoyed private swimming facilities. Dolphin Square's serviced apartments in SW1 were built with a pool in 1937, but are only available for rental on a three-year lease. Annually, around eight per cent of the flats, which are administered by a trust, become vacant .
If you are of more slender means (and proportions) you could pick up a property for around pounds 20,000 in Brixton's Tudor Close, where 100 studio flats nestle around an open-air pool. Suzy Clark has worked at the Woolwich's Brixton branch for two years, but has yet to sell a studio: "The flats are snapped up by developers. They're ideal for letting but are extremely small."
Blackheath is a greener, village-like enclave where pools seem less unusual. But William Hale, negotiator for Comber & Co, sees more pools than clients who want them. On his books, Mr Hale currently has two properties with pools, including one in Blackheath Park, on at pounds 1.2 million, which has an indoor and outdoor pool: "They are quite rare but we don't have clients waiting for houses with pools."
Mr Hale doesn't believe a pool detracts from a house's value and has never heard of anyone filling one in: "A pool is a luxury. A client may buy and say they'll put up with it but I bet they enjoy it when they're there. I certainly would."
A few miles from Blackheath lies Catford, known for its dog track - not for its plethora of pools. Yet walk down the Victorian terraced streets and you may hear splashes on a sunny day. Anne Eastwood has lived there for more than 20 years and, with husband George, installed a pool in the Seventies which their children and grandchildren still use.
Anne and her friends like lounging around by the pool but she would not dream of getting involved in its regular maintenance: "I leave that to George. It's like therapy; he loves it. He's always hoovering and pouring things in. If I think my friends will be round at the weekend I tell George to get hoovering and switch the boiler on. It gives him something to do."
Most Londoners, tired of toiling in grimy offices, head for the many open air communal pools dotted around the capital. On a grey day you could find yourself practising your synchronised swimming alone. But when the sun shines your relaxing swim can be marred by hordes of sweaty souls with the same idea. The Serpentine is stuffed, Highgate is heaving and a brimful of Brixtonites battle for towel space in London's coolest pool, The Lido.
Astute Londoners don't bother competing for swimming lanes. Behind their Thirties' semi in Forest Hill, Sara and Ray Dennis have a 200ft garden and, more unusually, a 20ft long swimming pool. They were attracted to the house for its garden not its "white elephant", which wasn't a big selling point. But their four children love telling schoolfriends: "We've got a pool."
The adults are less enthusiastic. Ray is "occasionally cajoled" into swimming by the kids, but Sara never uses it, despite its thick bubble wrap which conserves heat: "It's freezing. I'd fill it in tomorrow if I could. It's a waste of space. The kids use it a lot, but when their friends come to play you've got to keep a constant eye out. I'd rather have peace of mind."
The Dennis's pool has been used just once this year, but traditionally they enjoy hosting summer lunch parties where their friends can enjoy the pool. Does Sara's popularity soar in the summer? "I'm popular anyway!" Winter tends to be a time for the Dennises to visit friends with larger homes, and in summer Sara reciprocates.
Keith Moon-style excess is not found in Forest Hill. No cars have ever landed in the pool, although someone once rode their bike in, and the sole casualty so far has been a drowned baby fox discovered on return from holiday.
And maintenance? "We're terrible. We let it go green, but I worry about putting lots of chemicals in." The pool is 20 years old and they replaced the liner last year which cost around pounds 1,000.
A pool boosts popularity in (hot) summers, particularly with location agencies who pay daily rates of pounds 500. Penny Johnson of Location Works is always looking for pools within the M25 area, as most film crews are London-based: "The nicer and nearer the better." Penny views many pools around the Docklands and other London developments which are glamorous but often unavailable. Would she use a pool in Catford for fashion shoots? "Models in swimsuits need heated pools so if yours takes five days to heat up, you've got to plan in advance." Switch the boiler on, George.
Comber & Co, 0181 318 9666; Harrods Village, 0181 741 7401; Angel on the Green, 0171 359 5259; Tara Swimming Pools, 0181 244 4040; Location Works, 0171 494 0888