Close your eyes for a moment and imagine this scene not quite four years into the future: Boris Johnson, London's Mayor, stands shoulder-to-shoulder alongside Prime Minister David Cameron to announce that, in the month leading up to the capital's 2012 Olympics, the use of cars will be heavily restricted.

Cars, vans and lorries with odd and even-numbered registration plates will banned on alternate days to force Londoners off the road and improve air quality and eradicate traffic jams in time for the Games.

Uproar is probably the word to describe what would follow. The people of Britain will take almost anything but mess with their cars and you have a fight on your hands. Or would the British people see the light through the fug of pollution and the desperation of sky-high petrol prices and give it a try for the sake of the "greenest" Olympics in history?

Well, they have in Beijing, although, let's be honest, a say in the argument here is somewhat limited among a people who don't have the chance to vote for their leaders. But the odd-even number plate scheme has been in operation since July 20 and, although a dirty brown haze hangs over Beijing much of the time, air quality has not turned up as an issue at this Olympic Games, in spite of the occasional histrionics, like the USA cyclists who arrived in Beijing wearing rather dramatic face masks.

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The measures, being rolled out across 20 cities in China, have taken an estimated 3.3 million vehicles off Beijing's roads every day and it is said that 4 million people have taken to what they are calling "green transport modes", such as car sharing, public transport, cycling and good old Shanks's Pony, a rarely employed mode of transport in these high-tech times. Even the China office of BP, supplier of the devil fuel, has been handing out cash incentives to employees of 200 Yuan-a-month, which amounts to around £20, to get out of their cars.

It is not just the removal of pollution that has been attacked in pursuit of the "Green Olympics", but the roads are noticeably quieter with traffic jams a rare nuisance across the city. While Ken Livingstone, when he was Mayor, took the route of effectively slapping a fine on motorists every time they chose to drive into London through his Congestion Charge scheme (a moneymaker which, no doubt, will be adopted by other British cities soon) Beijing went for the clean cut. If cars and lorries are not on the road, then they can't pollute and they don't make the place look untidy either.

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To be fair, the Chinese authorities have put both their money and their reputations where their mouths are. For example, they slashed bus fares - you can travel across town for as little as 40p - and upgraded 19,000 buses and 66,000 taxis in Beijing alone while municipal governments in places like Qingdao, where the Olympic Sailing Regatta is based, have followed suit.

Hats off, too, to Du Shaozhong, deputy head of Beijing's environmental bureau, who led the way by putting his car in the garage so he now walks the 70-minute route to work daily. His actions alone triggered an epidemic of walking with around 250,000 Beijingers getting onto their feet.

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But the disruption must have been enormous. Factories and huge industrial plants have simply been shut down or moved on to improve Beijing's air, or required to conform by installing huge and, presumably, costly upgrades in environmental cleaning systems. Measures have even extended to corner shop dry cleaners, car repair shops and cafes and restaurants. In London, moving three sheds and a gypsy encampment usually provokes a public inquiry and a government statement, and Britain's population is not so easily convinced when their leaders issue the call to arms, particularly if it is going to cost them.

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Even the athletes are in on it and their Athletes' Village in Beijing has been winning environmental awards for its efforts in recycling and water management, a key issue out here in which the Beijing authories have made huge strides.

Parkland abounds, tens of millions of trees have been planted and just about every flat roof in the city now has a garden sitting on it, all huge efforts to improve the air quality and make this a clean Games.

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But how much of this Green Olympics malarkey is diesel smoke and mirrors? One of the official sponsors is McDonald's, serving burgers by the diesel-powered truckload and it is an established fact that beef production is one of the heaviest consumers of water, for example.

Or take any one of the hundreds of diesel-powered buses that ferry athletes, journalists and officials around Beijing and other key Olympic sites; how long do those buses sit idle with their noisy, smokey engines running, their exhausts belching fumes simply to power up the onboard air-conditioning systems? Or what about the huge fleet of 300 official cars running around the streets with air-conditioned dignitaries in the rear seats, doing mile upon unnecessary mile at the whim of VIPs.

And how much aircraft fuel was used to ferry - I don't know the precise number but let's guess at a minimum of 30,000 - athletes, officials and media people to Beijing, and that is not counting hangers-on and tourists, from all points of the globe?

Then there are the tonnes of rubbish we generate, the millions of meals we consume greedily, the gallons of water in plastic bottles we glug before we all turn around and fly home in our Jumbo jets with their airborn trail of emissions.

The rhetoric of the Beijing authorities - and, no doubt, London to come - is convincing and the effort has been nothing short of miraculous but, in the end, the words "Green" and "Olympics" simply cannot co-exist. Nice try, shame about the smog.