This week’s announcement by the UK Government that it is throwing its weight behind a proposal to build a third runway at London Heathrow may sound like decisive action on the surface, but serious doubts remain over whether this long-delayed airport capacity increase will ever actually happen.

After all, we’ve been here before. A decade has passed since then-Prime Minister Tony Blair’s Labour government backed the addition of a third runway at Heathrow. This backing was overturned when recently-departed Conservative Prime Minister David Cameron came along, fresh from flouncing around the Arctic doling out hugs to huskies in an attempt to convince the British public of his green credentials, and famously made his “no ifs, no buts, no third runway” pledge.

The most recent U-turn came yesterday when current Conservative Prime Minister Theresa May’s government announced its support for an additional runway at the congested capital city gateway. Ministers stressed that boosting airport capacity would show the world that the UK is “open for business” – an important point to make following the country’s decision in June to turn its back on the European Union.

As anyone who has flown into Heathrow and circled the skies above London awaiting a landing slot will attest, the situation as it currently stands is not ideal. Heathrow is full and air travel demand is growing, creating a mismatch that can only be good news for nearby northern European hubs such as Paris Charles de Gaulle and Amsterdam Schiphol. But there is no easy resolution that will satisfy economic, business, residential and environmental concerns.

Even key figures within the prime minister’s own cabinet were quick to cast a shadow over the likelihood of a third runway becoming a reality, with UK Foreign Secretary Boris Johnson yesterday describing the project as “undeliverable”. Johnson has been vocally opposed to expanding Heathrow in the past, preferring instead a shelved proposal to replace it with an all-new airport in the Thames Estuary.

But the most vocal opposition comes from environmental campaigners and local residents, and this looks set to dog the expected year-long consultation period that will precede any binding Parliamentary decision on Heathrow.

Local councils representing residents living under the Heathrow flight path have vowed to work together and step up their efforts to try and prevent a third runway from being built. And UK-based environmental NGO Aviation Environment Federation (AEF) has described yesterday’s announcement as a “dark day for communities and for the UK’s chance of tackling climate change”.

However, AEF director Tim Johnson tells RGN that even if Parliament votes in favour next year, it will be “a minimum of two-and-a-half years” beyond that before any final decision on whether to build a third runway would be taken. Heathrow would have to make its own application for development, which comes with its own public enquiry process, and “given what we’ve seen…there is no way this is going to progress smoothly”.

By that point, the UK will be ramping up for another general election and this political hot potato will start burning politicians’ hands again.

“There are no easy political answers,” says Johnson, adding that the “same questions remain” over air quality issues, climate change commitments and noise implications. “I’m not confident this is a final decision.”

If opposition from politicians, environmentalists and local residents doesn’t cast sufficient doubt on the prospects of a third runway ever being built, the reaction from the users of the planned infrastructure project – the airlines themselves – has been lukewarm at best. IAG, the parent company of Heathrow’s biggest customer, British Airways, says in a statement that while it welcomes the decision, it will fight to ensure that the additional capacity does not end up being paid for by airline passengers.

Meanwhile, London Gatwick Airport is waiting in the wings with its overlooked proposal to build a second runway on standby, in the hope that anti-Heathrow campaigners get their way. The airport’s chief executive, Stewart Wingate, says that Gatwick “stands ready to proceed when the time comes”.

Whether that time will come is anybody’s guess.