Leading article: Another runway at Heathrow is no solution

It is time to be ambitious, to build an all-new airport in the Thames Estuary

And so, with an otherwise far from radical Cabinet reshuffle, the incendiary issue of a third runway at Heathrow is back on the political agenda. Manifesto commitments and the Coalition Agreement might rule out any such plan in this Parliament. But the demotion of former Transport Secretary Justine Greening – MP for Putney (under the noisy flight path) and avowed opponent of expansion – is a sure sign of a change of emphasis, as are the remarks from the newly installed Conservative chairman that "all options" are on the table.

So they should be. Indeed, the independent review announced yesterday – to be conducted by Sir Howard Davies and report after the next election – is to be warmly welcomed. For too long the vexed question of long-term aviation policy has been held hostage by an unholy alliance of Nimbyism, lobbying and short-term politics. It can only be hoped that Sir Howard's deliberations can break the stalemate.

One thing is sure: Britain can no longer afford to do nothing. Heathrow, Gatwick and Stansted are all running at or near capacity, even as rivals are growing – in Frankfurt, Amsterdam and Dubai – particularly in relation to China. Britain has much to gain from keeping its status as an international hub: in prestige, yes, but also in hard cash, in jobs, and in the boost to London as a business location.

The change of heart from David Cameron and his Chancellor on the third runway is, perhaps, hardly surprising. After all, it is the option favoured by the business lobby and George Osborne's reliance on a private sector recovery is becoming ever more desperate as the economy continues to slide. Expanding Heathrow is not the right answer, though.

The politics is tricky enough, with Zac Goldsmith, whose voters live under the flight path, threatening to force a by-election and Boris Johnson branding the plan "mad". Uproar over noise is not the material point, however. Rather, it is that demand will swiftly outstrip even a third runway, rendering the multi-billion investment little more than a costly stop-gap. Within just a few years, the same problem will resurface.

If not a third runway, what then? Put simply, the time has come to be ambitious. Too many of the proposed solutions – from a high-speed train link between Heathrow and Gatwick (expensive and unworkable) to another runway at Stansted (a Nimby hornets' nest worse even than that at Heathrow) – offer at best a partial fix, at worst none at all. Better to make a once-and-for-all decision and press ahead with plans for an all-new, four-runway hub in the Thames Estuary, either on the Isle of Sheppey (so-called "Boris Island") or on the Isle of Grain (as proposed by architect Norman Foster), complete with super-fast transport into London.

True, there are complications. A price tag upwards of £20bn means concerted wooing of private-sector investors. The impact on local wildlife will also need careful attention. As will the implications of closing Heathrow and shifting the jobs east. But all are relatively short-term concerns in comparison with the lifespan of an airport. And the benefits of flight paths over the Thames rather than the city, of space for further expansion, and of a planned transport network all weigh heavily in favour. There is also much to be said for significant infrastructure spending in these economic doldrums; even a building programme that would not start for several years would be a boost.

Mr Cameron is right that all options deserve consideration, and right to commission a full review. But his apparent tilt away from support for a Thames Estuary scheme and back towards Heathrow looks disconcertingly like a failure of nerve. If there was ever an issue demanding a far-sighted response, this is it.