The revelation in Wednesday's Telegraph that a consultation on an airport in the Thames Estuary is to be launched in March has Westminster and the City of London buzzing.
Boris Johnson has been waxing lyrical about the idea for years, despite fierce opposition from many MPs in his own party. The plans already exist and some striking computer-generated images have been produced.
Any option is likely to have its opponents, but the general consensus is that something has to be done about airport capacity in the south east of England.
Heathrow is full to bursting. It regularly runs at 99% of capacity and even the smallest hiccup can often lead to dozens of delays and cancellations. As Boris Johnson put it on the Today programme on Wednesday morning, "It's fundamentally in the wrong place," on a low-lying part of west London where fog is an annual problem in the winter.
On most days because of prevailing westerly winds (planes almost always take-off and land into the oncoming wind), increasingly large passenger planes come in to land over central London, leading to the incessant whine of engines above the capital 19 hours a day. That noise becomes increasingly deafening the closer you get to the eastern approach to the runways.
The noise nuisance could get worse. Since November 2011 Heathrow has been piloting a scheme called "mixed mode", whereby the airport's two runways are simultaneously used for takeoffs and landings during congested periods.
Colin Matthews, chief executive of Heathrow's operator BAA, told the Today programme on Radio 4 that the consultation should include revisiting the option of a third runway there. But this is a non-starter politically. Although Labour and the Tories disagreed about it before the last election there's now a settled view among the main parties that the runway will never be built. Labour formally abandoned the policy at the end of October 2011.
But Matthews was correct when he claimed that: "Frankly every single option has difficulties."
The options include an airport on the southern banks of the estuary, or a more ambitious plan to construct an artificial island in the estuary itself, a plan favoured by the Mayor of London and inevitably dubbed "Boris island".
But building a major airport east of London would mean areas along the Thames Estuary - many of which are super-marginal politically - would one day begin to experience the noise, pollution and traffic already blighting the Heathrow area. The government would face immense opposition from people living along the estuary, with MPs lobbying against it being built. Tory MP for Thurrock Jackie Doyle-Price wrote on HuffPost UK in September that an estuary airport would suffer from the same fog and pollution problems as Heathrow. She also believes that if a major airport were built then Heathrow would have to be closed, because the UK can only support one major international hub. Any airport in the estuary would probably mean much of east London experiencing the roar of take-offs (thanks to those prevailing westerly winds).
Within the coalition there is an obvious split looming with the Liberal Democrats opposed to anything resembling "Boris Island", but as the Mayor of London pointed out on the radio on Wednesday morning, "George and Dave" - that's blokey Tory-speak for the PM and Chancellor - have come around to the idea of a new airport. The two men have realised that the UK economy needs to have a major 21st Century global hub - competing with Charles de Gaulle in Paris and Schipol in Amsterdam, both of which are already larger and built in much more sensible locations than Heathrow.
But we're getting a bit ahead of ourselves. The consultation on a Thames Estuary airport will form part of a wider discussion on the UK's aviation infrastructure, due to be launched in March. That will take a while. The consultation on HS2, recently completed, took nearly a year. That was one of the largest-ever consultations ever undertaken by the Department for Transport, with thousands of responses.
Given a major new airport in the southeast of England would likely stir up just as many reactions as the high-speed rail project, it seems likely the "Boris Island" consultation process would take just as long, so ministers wouldn't be in a position to green-light any airport until the spring of 2013, well into the latter-part of the current Parliament. Rush the consultation and you then have to factor in legal objections and challenges, feasibility studies and "events', and you're looking at a decision being finalised perilously close to the next general election.
It's not clear how Labour will respond to the plan - they looked at it when they were in government and rejected it, in favour of the third runway at Heathrow. Ken Livingstone is on-record as describing Boris Island as a "crazy" scheme, and local Labour groups in Essex and Kent have been campaigning against it. Whether Ed Miliband would gamble economic credibility against the electoral boost among not-in-my-back-yard types remains to be seen.
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