The Sun says today that there will be a Commons vote on Heathrow expansion in June.  ConservativeHome is told that it will be “then or thereabouts – certainly this summer”.  The Airports Commission recommended the airport’s proposal for a new north-west runway.  The Government backed the Commission.  Today, the Transport Select Committee supports the Government in principle: “we conclude that the Government is right to pursue development at Heathrow and accept the strategic arguments the Government has made in favour of its preferred scheme,” it says in a new report.  This is part of the process, including a further consultation, that Chris Grayling announced last September.  He indicated then that the Government would produce a final proposal for a vote “in the first half of 2018”.  We understand that it would have been earlier had there not been a delay in establishing the Select Committees.

Put like that, the process sounds painstakingly scrupulous or frustratingly slow, according to one’s point of view.  But it is only part of a much longer story.  Other countries made major airport expansions; the Thatcher, Major, Blair and Brown governments did not.  By the time of the Coalition, it was agreed that Something Must Be Done.  The big battalions were for Heathrow.  Conservative MPs in south-west London and elsewhere in the capital weren’t.  David Cameron set up an Airports Commission to make a recommendation – conveniently timed for after the 2015 election.  The Commission duly backed the Heathrow north-west runway scheme unanimously…by which time Cameron had won an unexpected majority, and there were even more unhappy Tory MPs in south-west London.  Then came the EU referendum and last year’s general election.

In consequence, the number of Conservative MPs in south-west London has been reduced a bit, and the next election isn’t due until 2022.  The big battalions are still for the Heathrow scheme, as the Select Committee’s report confirms.  The stocks are sold, the press is squared, the middle class is quite prepared – except in the suburbs near Wimbledon Common and Twickenham Stadium and Richmond Park, and so on.  May and Chris Grayling want to get on with it.  They calculate that they have the numbers: that any Tory rebellion will be offset by Labour and SNP support.  Perhaps the Downing Street view is that voters in south-west London are expecting a vote for Heathrow anyway, sooner or later, and that the London local election results will be dire in any event.  Zac Goldsmith can scarcely call another by-election.  And Boris Johnson will not “lie down in front of the bulldozers” to stop expansion, as he once promised to do.

Not that they will be juddering into action any time soon.  Britain has a big capital city, a relatively crowded south-east, a planning system that moves slowly, and a tenacious attachment to litigation.  Even if none of the forthcoming legal appeals are successful, we won’t see that new runway for a long time yet.  For opponents of Heathrow expansion, developments will seem less slow.  They argue that the whole process was set up to further the conventional wisdom, which in this case, as so often elsewhere, will turn out to be wrong.  They add that the costs of the plan don’t add up, since Heathrow won’t pay for a runway it can’t charge passengers for, and that the Select Committee report points out that the circle on costs needs to be squared.  It also recommends “several additional conditions of approval…on air quality, surface access, connectivity, costs and charges, noise, community impacts, resource and waste management.”

That’s a long list.  And, in a sense, the committee report itself needs to be squared.  On the one hand, it commends the Heathrow scheme in principle.  On the other, it expresses a mass of qualifications about the practice: “before votes in Parliament to Airports National Policy Statement approve a final NPS, we would like to see evidence to demonstrate that the Northwest Runway scheme is both affordable and deliverable and that steps are being taken to address the valid concerns we heard in evidence about the high cost of the scheme and the significant risk that costs will rise”.  Is concentrating expansion at Heathrow really necessary?  Should the environmental burdens not be spread more widely, with Gatwick bearing some of them, while also gaining from an expansion of flights, visitors and business?  Or should expansion not be pushed east, to Stansted, or north towards Birmingham?  What about Boris Island?

The questions roll on.  One view this morning is that the Select Committee report has exposed the scheme’s Achilles heel: costs.  There is an inglorious tradition of big infrastructure projects running over budget.  But the politics of Heathrow expansion looks a lot like the politics of, say, HS2 (as does its budgeting, some will add).  A number of MPs with local interests are opposed.  They are passionately committed to their constituents’ cause, and follow the arguments in detail.  Most MPs do not.  They have been persuaded that the most simple answer is also the right one – to grow Britain’s biggest airport further.  May and Grayling’s cry will be that Britain must raise its infrastructure game to make the most of Brexit.  For years, the airport expansion decision has itself been like one of those planes that seem to circle Heathrow ceaselessly, with groaning passengers yearning to land.  Like them, many voters will want to get a move on.