Few things are as unpopular as a tax rise. It's strange, then, that London's latest stealth tax has won all-round applause. The mayor is raising the congestion charge levied on four-wheel-drive vehicles - known as 'Chelsea tractors' in London - possibly the most unpopular creature in the capital, not including traffic wardens. Not a day goes by without spotting a 'Bad choice of car' or 'Is this car necessary?' sticker on one, or hearing rival motorists, pedestrians and cyclists rudely motioning, or remonstrating with drivers of the growing bete noire of London environmentalists. About 20 per cent of cars in London are heavy-polluting, petrol-guzzling four-wheel drives, a now much-derided symbol of wealth and status. It's the highest ratio anywhere in Britain. Given the recent wholesale conversion to all things green - following last month's report on climate change by Sir Nicholas Stern - many wonder how long this boom can last. Not least now that the mayor and individual councils have declared war on the behemoths. In Richmond, in affluent southwestern London, the council has lifted resident parking permits fourfold for large cars and four-wheel-drives, to GBP300 (HK$4,559), claiming they take up more space so they should pay for it. The wealthy borough of Kensington and Chelsea, where residents are twice as likely to own a four-wheel-drive as other Londoners, plans to follow suit. So does Chancellor of the Exchequer Gordon Brown, who plans to raise the annual car tax for four-wheel drives nationally to GBP210. But the biggest hit, and the possible deal breaker for most owners, was a triple whammy from Mayor Ken Livingstone, the man who once described urban four-wheel-drive motorists as 'idiots', and whose personal, and very public, crusade is to force them off the road. Mr Livingstone aims to raise the daily charge for such vehicles entering central London from the current GBP8 a day to GBP25 by 2010, saying that fewer four-wheel drives would cut emissions and ease congestion. He also plans to take the 90 per cent discount on the annual charge for all drivers living within the zone away from owners of fuel-guzzling vehicles. The move will bring the annual expense of running a Chelsea tractor in central London up to GBP5,500. If that's not enough, he plans to extend the charge area into Chelsea. Ouch! The mayor is unmoved by criticism, saying owners have three years to trade in their cars for more efficient models. It is a deft political stroke. The increase will also hit many ordinary family vehicles, but few people seem to care. So deliriously happy are they that those visible symbols of wealth are being walloped, they have forgotten their own punishment.