First, I think I need to correct Tim's argument, which Charlie links to, that opposition to the third runway is "crucial in the battle to win many seats under Heathrow's flightpath". The evidence for that statement is very weak. Anthony Wells, at the excellent UKPollingReport blog, highlights the underlying figures in Greenpeace's poll on the subject: "Of the people who say it would make them less likely to vote Labour, the large majority say they would vote Conservative or Lib Dem tomorrow anyway. Too many people in questions like this are committed voters who are just using it to send a message, not people whose vote is actually up for grabs."
Many voters under the Heathrow flightpath, in West London marginals, may dislike the idea of another runway but those who care enough to even think about changing their vote on that basis are already voting Tory or Lib Dem (and the Lib Dems also oppose the new runway). On the other hand, there are Labour voters, in those very marginals, who are more committed to that party because of the possibility of a third runway: "Of the people who say a decision to build a third runway would make them more likely to vote Labour, the overwhelming majority are people who say they would vote Labour already." Unless we really think that the Conservatives' primary objective in West London should be to defend their core vote, the policy isn't a political winner.
I've written, at length, before about the policy of putting in place a high speed rail link and blocking a new runway at Heathrow. There is a huge range of reasons why the policy doesn't stack up:
High speed trains aren't a green panacea. George Monbiot, who hates flying so much he compares it to child abuse, has said that high speed trains create more emissions if powered from conventional sources (which they would be in Britain). Getting major new rail lines through the various stages of planning will take forever, Britain will suffer a shortage of capacity in the meantime. Planes circling above London waiting for a landing slot aren't doing much to reduce emissions. New rail lines will represent an extremely poor substitute for a new runway if and when they are completed. You won't avoid the need to upset locals, and use compulsory purchase, as the line will need to be driven through hundreds of miles of countryside and into the major cities the lines are supposed to connect.
The question I'd ask Charlie, in particular, is why should anyone on the centre right be in favour of using regulations to block private industry spending £13.3 billion on a major infrastructure project, just so that £15.6 billion of taxpayers' money can be spent instead?
