Heathrow expansion: How plan for third runway could become a political football again

Politics Explained: Plans may have been filed for the airport, but that may change if MPs push back against development again

Finally, after decades of prevarication, talk of airport expansion in southeast England looked as though it was turning in to action. At 8am on Tuesday 18 June, Heathrow filed its flight plan for developing a third runway. It revealed the intention to increase flights by up to 10 per hour even before the new strip is completed, and the ambition to raise passenger numbers by 77 per cent ultimately to 170,000 a day.

One primary school, 761 family homes and three sets of allotments will be demolished and relocated. Or will they?

“A third runway will fail both London and the UK on every level,” said Boris Johnson, the man likely to become prime minister.

As foreign secretary, he managed to dodge the overwhelming parliamentary vote approving the choice of Heathrow for expansion with a rather random visit to Afghanistan on the day the decision was rubber-stamped.

Yet everyone from his Uxbridge and South Ruislip constituents to his colleague and backer Zac Goldsmith will expect him to use his ascendancy to Downing Street to kick the airport expansion debate back to its traditional location in the long grass. An instruction to the Department for Transport to look again at plans for a Thames Estuary airport – as championed by Mr Johnson while London mayor – will do the trick.

With unprecedented political uncertainty, the views of the other parties will come into play if the new prime minister is forced into a new general election.

John McDonnell is both the shadow chancellor and the “MP for Heathrow” – the airport lies within his constituency. Along with the mayor of London, Sadiq Khan, he is likely to reopen the possibility of a second runway at Gatwick instead: expanding the Sussex airport would impact far fewer local residents.

But if a new Labour-led government required support from other parties, airport expansion could become a red line for any coalition.

The Liberal Democrats manifesto for the 2017 election was clear: “We remain opposed to any expansion of Heathrow, Stansted or Gatwick and any new airport in the Thames Estuary.”

And although the SNP was initially in favour of expanding Heathrow, because of the promises of better connectivity for Scotland, Nicola Sturgeon’s declaration of a “climate emergency” indicates that the first minister’s view has changed.

On a BBC radio programme a few hours after the Heathrow master plan was announced, I was asked whether I thought the airport would have a new runway in 2050, the date to which all forecasts are focused. Yes, I said – but I am not sure that it will be ready, as planned, by 2026.