The Tory election manifesto promised nothing more than “to respond to the Airports Commission’s final report” which it could do by putting the recommendations to a vote in the Commons, though it is impossible to predict how this would go. Mr Cameron must dearly hope that the Airports Commission makes his life easier by opting for Gatwick. But even if it does, would MPs support it in a free vote? Labour has been all over the place on a third runway at Heathrow but it was once official party policy; meanwhile the SNP support it. Polls show that most MPs are in favour of Heathrow.