Barring a last-minute change of heart, the government is about to make a transport error of monumental proportions. A parliamentary rooftop protest last week by the pressure group Plane Stupid generated headlines but little else. The government will soon announce a third runway at Heathrow, already the world’s busiest international airport. Even as the Queen opens the fifth terminal this month, plans for a sixth are in the pipeline. You do not have to be a protester to realise there is something spectacularly wrong with an extra 200,000 annual flights at Heathrow by 2020, given existing congestion and chaos. That, however, is what Gordon Brown intends to do.

We have argued before that the government should take its cue from successful moves by other countries, which have opened new airports away from centres of population with fast transport links. Our preferred solution, despite some environmental objections, would be a new airport in the Thames estuary, east of London, for less than the cost of the 2012 Olympics. That, however, is too big an idea, and has been rejected on grounds of cost, or birdlife, or inconvenience, when all these things are surmountable with farsighted leadership. Transport policy in Britain is governed by dull incrementalism. Heathrow, London’s airport courtesy of an accident of geography, will carry on expanding.

It exposes the hypocrisy of policymakers when it comes to “green” and quality of life issues. Many of the increasing numbers who live on the Heathrow flightpath are about to have their lives made even more miserable by noise and atmospheric pollution. Yet many, if they are unfortunate enough to live in Ken Livingstone’s west London catchment area and drive the wrong car, are about to be made to pay £25 a day, ostensibly to help save the planet. Any government that presides over the mindless expansion of Heathrow cannot seriously claim to be green. Remember that the next time you hear Mr Brown posturing about the environment.