Heathrow's expansion may have been approved – and the business case for it was overwhelming – but the real action is yet to come

As the saying goes, this is not the end of the matter, though it is perhaps the beginning of the end. Even if things go relatively smoothly, there will still be sufficient turbulence to delay the first operational flights for a decade or so

Boris Johnson has vowed to oppose the expansion of Heathrow, despite the Government's decision (Reuters)

The decision to expand Heathrow was, even without hindsight, always inevitable. Government after Government has fudged the issue, palming it off to debates and inquiries, fearing Cabinet revolts or the loss of vital parliamentary seats, or just genuinely dithering. Much time has been wasted.

There was always a certain amount of artifice about the debate. The option of an entirely new airport, so-called Boris Island, had more merit than it was often granted, because who in their right minds would choose Heathrow as a location if we were starting from scratch? The claims of Gatwick were very real too. Indeed there is certainly a case for revisiting expansion at Gatwick in parallel with Heathrow – and in parallel with regional airports, including those named after John Lennon, Robin Hood and George Best.

However, compared to even all these combined, the economic and business case for Heathrow was overwhelming. Nowhere else in the country has a comparable existing infrastructure, the skills base, the experience and, above all, the base as a viable hub for the rest of the UK, and, indeed, the rest of the world.

The case against Heathrow was primarily environmental, and it was strong. But if the green argument is judged to be paramount, then we would not build new capacity at all, and that would have very serious consequences for economic growth, both in that part of England and across the UK. With the new treaty on climate change, for example, we have committed the nation to a wider agenda of fighting climate change, in which aviation plays its role alongside energy, road transport, industry and so on. The marginal difference on pollution and noise between Gatwick and Heathrow was never going to sway the advantage, as Howard Davies showed in his report, a thorough and objective run through of all the issues.

Politics, now, comes to the fore once again. As the saying goes, this is not the end of the matter, though it is perhaps the beginning of the end. Even if things go relatively smoothly, there will still be sufficient turbulence to delay the first operational flights for another decade or so. By that time Britain’s future as a trading nation will be much clearer, and will be much strengthened by a renewed and expanded Heathrow (and Gatwick too, perhaps). That will be true whether we stay in the EU or not.

The first cross-wind will be the by-election forced by the resignation of Zac Goldsmith. Here, at least, is a politician who is prepared to stand by his pledge to his constituents. Much good, though, it will do them, Mr Goldsmith or his (former) party. The voters of Richmond might well be expected to oppose more noise: whoever wins will prove a rather obvious fact. We do not live in a country, yet, where every borough possesses a veto over the economic progress of the entire nation (including far less wealthy and thriving places with SW and TW post codes).

Whether Mr Goldsmith cares or not, the by-election will principally act as an opportunity for the Liberal Democrats to regain the seat they lost to him in 2010. After their encouraging showing in Witney, after the resignation of David Cameron, and some other evidence of life in what was deemed to be a dead parrot, a Liberal Democrat breakthrough in what was once solid territory of theirs would be a timely boost. As Ukip sag and Labour continues to look inward, the Liberal Democrats could also capitalise on the substantial anti-Brexit feeling in this prosperous corner of the capital. Their claim to be the repository of choice for the protest vote would be re-established. The Lib Dems have not, in fact, gained a seat form the Conservatives at a by-election since May 2000.

The message that the Liberal Democrats were back in business would be extremely unwelcome to the Prime Minister and her party; with a Commons majority of 12 and some controversial proposals, Theresa May needs all the votes she can find.

Not that the by-election in itself will make any difference to the Heathrow expansion. Nor will the slightly theatrical objections of local MPs (for these purposes) Boris Johnson and Justine Greening. Nor, most likely, will the many protests and residents chained to trees we’ll see in coming years.

Contrary to Mr Johnson’s assertion, Heathrow expansion is eminently deliverable. Like Brexit, the real action is yet to come. One day the story will surely make a great in-flight movie, though perhaps a slightly overlong one.