The Prime Minister presumably believes we face a critical shortage of airport capacity in London. Why else would he signal a possible U-turn on what was a headline pre-election promise? He knows that one reason west London voters backed the Conservatives in the last general and local elections was his decision to rule out any prospect of building Labour’s 3rd runway at Heathrow.

But if that is how he feels, why on earth would he commit to doing absolutely nothing for three years? I am yet to meet anyone who believes an airport review should take anything like so long; indeed the majority of options have been studied to death. Moreover, it wouldn’t simply be a three-year delay. Add a lengthy planning process, and it could be more like six years before work even begins.

If we face a crisis of under-capacity, and if the priority is getting the economy going, it is hard to imagine a more useless policy. A six-year delay will cause paralysis across the board, with businesses not knowing where to invest, residents not knowing how their lives may be affected, and no possibility of informed decisions relating to surface transport infrastructure. Everyone, no matter what solution they favour, wants a decision.

The dithering isn’t simply bad for the economy. For voters beneath Heathrow’s flight-path, this ambiguity looks like a hidden green light for expansion. Come the election, the Conservative Party will feel all the electoral downside it is trying to avoid. In other words, whichever genius thought Heathrow could be kicked into the long grass has guaranteed that it will become the defining election issue in the many constituencies affected by it.

Meanwhile, to voters beyond the flight-path, and to businesses, lobby groups and the like, this extraordinary position can only reinforce the impression of a government crippled by fear of taking difficult decisions, and so worried about fronting up to voters that it daren’t reveal its policy until voters can no longer have their say. It is shockingly bad politics.

The irony is that the government’s review will almost certainly rule out Heathrow expansion.  The economic arguments will not justify subjecting 2 million residents to increased aerial bombardment. Making room on London’s congested roads for an extra 25 million road passenger journeys to and from Heathrow will prove nightmarishly difficult. And privately, it is agreed that if the arguments in favour of expansion are correct, we will need a fourth runway too. A cursory glance at the map shows how complicated and expensive that would be.

Most importantly, the arguments being used to bulldoze the government into a U-turn are grossly exaggerated. Heathrow already has more flights to business destinations than any other airport in Europe. More passengers fly in and out of London than any other city in the world. We are well-connected, we have ample capacity. The problem is that we don’t use our capacity well. If we want to preserve Heathrow’s hub status, we need to stop clogging it up with point-to-point flights to places such as Cyprus and Greece, which between them account for 87 weekly flights, and contribute nothing to overall connectivity.

We also need to discourage operators guarding their slots by flying half-empty planes. Heathrow has terminal capacity for an extra 20 million passengers, and with fuller and, in places, bigger planes, we’d be able to accommodate many more. In addition, we need to encourage a shift from air to rail wherever possible. Every week, for example, there are more than 300 flights from Heathrow Brussels, Manchester, Newcastle and Paris. In time, a better high speed rail network will help.

These measures would relieve pressure on Heathrow, but by improving links to other airports, we can do more. For example, Stansted is massively underused, by nearly 50 per cent, and with proper rail links to the City, it would be the natural place for business flights. There is no reason why we couldn’t facilitate a two-hub approach, with Heathrow catering (broadly speaking) for western-facing flights, and Stansted catering for eastern business flights.

It has been argued that these measures are inconvenient and complicated. Perhaps, but the government will find that they aren’t nearly as inconvenient as the alternatives.

Tickets are still available to the Spectator’s debate on expansion at Heathrow, which will be held on Monday 26 November at Savoy Place in London. A panel of experts - including Boris Johnson’s right hand man, Daniel Moylan, and influential Tory MP Graham Brady - will discuss the question, ‘No ifs, no buts. Heathrow must have a third runway.’  For more information on this event, including tickets and directions to the venue, click here.

Zac Goldsmith is the Conservative MP for Richmond-upon-Thames.

Tags: Airports, Conservatives, David Cameron, Heathrow, London, Spectator debate, Zac Goldsmith