The political obstacles to building a third runway are insurmountable

Heathrow expansion is a fantasy that will never be realised

Heathrow expansion is a fantasy that will never be realised

The long-awaited Airports Commission report released this morning is unanimous in its support for a third runway at Heathrow, saying that it is the "best answer" to the UK's aviation needs.

Gatwick expansion is described as "plausible" but not ideal. Meanwhile, Boris Johnson's rival plan for a new hub airport is summarily dismissed as "unfeasibly expensive, highly problematic environmentally and hugely disruptive for businesses and communities".

Yet while Johnson's scheme to build four runways next to 1,500 tonnes of unexploded munitions may seem utterly hair-brained, it is actually Davies proposal which is the real fantasy bid.

At first look, the case for expansion at Heathrow seems attractive. Unlike all other UK airports, Heathrow is running at or close to capacity. Business support for a new runway is strong and the public demand to use the airport is growing.

Yet the political obstacles to actually building a third runway at Heathrow are so large you could see them from space. Let's go through them one by one.

Trust

The prime minister David Cameron was elected on a promise to oppose expansion at Heathrow, saying in 2009 that: "The third runway at Heathrow is not going ahead, no ifs, no buts."

This is about as categorical a pledge as a politician could make. If he were to break it, it would be even more damaging to his credibility than Nick Clegg's broken promise on tuition fees. Last night 'senior government sources' briefed the Telegraph that there is little chance Cameron will break his promise to voters.

Party management

Heathrow expansion is opposed by Conservative politicians locally and nationally. Both the current Conservative mayor of London and his likely successor Zac Goldsmith are vehemently opposed to a third runway. Today Goldsmith said he would resign his Richmond seat if expansion is given the go-ahead. Johnson has also been touring the studios pledging to fight expansion tooth and claw.

Heathrow expansion would also face massive opposition within the Tory Cabinet. Philip Hammond, Theresa May and Justine Greening are all believed to be strongly opposed to a third runway as are many other senior Conservatives. If Cameron pushes ahead with Heathrow expansion it would cause a massive internal revolt. And this is even before you consider the huge local opposition from Conservative councils expansion would provoke. Again, it is simply impossible to see how Cameron could fight this battle and win.

Electoral politics

Heathrow is surrounded by a series of marginal Tory constituencies which would be directly affected by Heathrow expansion. The west London vote has also been decisive in all four previous London mayoral elections. The London Assembly has had a cross-party opposition to Heathrow expansion for over ten years. No mainstream mayoral candidate has ever stood on a platform of supporting a third runway and both the current Tory mayor and his likely successor are opposed.

If Cameron were to back Heathrow expansion it would be a major threat to his party's electoral prospects. By contrast, the constituencies around Gatwick are much more solidly Conservative. Opposition within government and City Hall to Gatwick is also much more muted. If Cameron is committed to expansion, then it is far easier politically to do so at Gatwick or elsewhere.

Environmental impact

Buried in today's report is the news that a third runway would increase noise pollution for local people by 50%. The new runway would also increase already illegal levels of pollution and bring much of suburban west London to a permanent grinding halt. The current road network already struggles to cope with demand produced by Heathrow. Further expansion would be impossible to deliver, without bulldozing and tarmacking over whole communities both at the site of the new runway and in the wider area. And this would all be in the face of probably the largest environmental protests ever seen in the UK. Davies' recommendations today to limit night flights and impose a "noise levy" would not even touch the sides of local opposition.

Time

If despite all this Cameron did plan to back Heathrow expansion then today would have been his best chance to do so under the cover of Davies' report. The fact he has delayed his response until the end of the year, suggests he has other plans. Even if that's not the case, Cameron is due to stand down within a few years, with bookies making Boris and May his two most likely successors. Both are opposed to a third runway. Even if Cameron were to take the politically foolhardy decision to expand Heathrow, he would be long gone before even the first spade hit the dirt.

In fact the more you look at Heathrow expansion, the more impossible it appears and the more attractive the alternative options become.

Of course one of the alternatives not considered by Davies is to resist expansion altogether. Nine out of the ten most popular UK airports are currently running well under capacity and overall aviation passenger demand in the UK has barely risen in the past ten years. Rather than continually pouring more water into Heathrow's already overflowing bucket, it would make far more sense to improve connections to – and use of – all those airports currently lying half empty.

Yet even if you accept the need for expansion, Heathrow is clearly the least politically and practically viable option.

In fact so stratospheric are the obstacles to expansion in West London, that even Boris's totally bonkers plan to persuade millions of migrating birds to leave the Thames estuary looks vaguely feasible by comparison.