It is 13 years since the then transport secretary Alistair Darling published a white paper supporting a third runway at Heathrow. Ever since, senior figures in both main parties have argued for aviation expansion. But politics has prevented a decision.
The last Labour government approved the construction of a third runway (nearly leading to the resignation of Ed Miliband from the cabinet) but the coalition cancelled the project when it entered office. Six months before becoming prime minister, David Cameron, with an eye to must-win marginals, declared: “The third runway at Heathrow is not going ahead, no ifs, no buts”. It was a promise, not least after witnessing the damage that Nick Clegg endured over tuition fees, that he was not prepared to break. But Cameron, in common with George Osborne, continued to regard another runway, at Heathrow or elsewhere, as essential.
The Airports Commission, established in September 2012, was designed to provide political cover for a decision. By deferring its recommendation until after the general election, it ensured Cameron avoided breaking his pledge (which was not repeated in 2015) and prevented aviation becoming a campaign issue.
In July, the commission endorsed a third runway at Heathrow and the government promised to respond by Christmas. But as that deadline approaches, all the signs are that a final decision will once again be delayed. Cameron will likely cite concerns over air quality as justification for the postponement. But it is his political motives that are clearest. The Conservatives’ London mayoral candidate, Zac Goldsmith, is an implacable opponent of a third runway and has vowed to resign as an MP if the project is approved. By delaying a decision until after the mayoral contest in May 2016, Cameron could avoid a dramatic split with the environmentalist (though sources say Goldsmith is still prepared to resign if the Prime Minister backs Heathrow with pre-conditions). International Development secretary Justine Greening is another third runway opponent and has not ruled out leaving the cabinet over the issue.
Some in Labour would like to attack the government for its epic procrastination. In July, as acting leader, Harriet Harman told Cameron that her party would vote in favour of a third runway if he brought forward legislation. But the election of Jeremy Corbyn means Labour is now even more divided than the Tories over the project. Corbyn has publicly rejected a third runway, while John McDonnell, whose Hayes and Harlington constituency lies under the flight path, is perhaps its most vehement opponent. In 2009, he was suspended from the Commons after picking up the mace in protest at the government’s decision. Corbyn and McDonnell are joined in opposition by Labour’s London mayoral candidate Sadiq Khan.
But with some frontbenchers, such as former shadow transport secretary Michael Dugher (now shadow culture secretary) in favour, a free vote, as in the case of Syria, could be required. Almost 30 northern Labour MPs and nine in London, including former mayoral candidates David Lammy and Gareth Thomas, support a third runway and have appealed to shadow transport secretary Lillian Greenwood to endorse the project. They are backed by the GMB and Unite unions, which, as on Trident, are at odds with the leadership on this issue. For Corbyn, as much as Cameron, then, there is every incentive to at least delay a divisive decision until the new year.