Why are we asking this now?
Backbench rebellions, unrest within the Cabinet, fierce opposition and regular bouts of direct action from the green lobby – the battle to create a third runway and sixth terminal at Heathrow Airport has it all. The latest scheme designed to scupper the project has even seen celebrities join the fight. The actress Emma Thompson and the comedian Alistair McGowan have joined campaigners, including the Tory environmental adviser Zac Goldsmith, the Greenpeace director John Sauven and the Liberal Democrat MP Susan Kramer, to buy land in the middle of the proposed site of the runway. The tactic has been used in the past to protect forests and fight road-building schemes.
What do they intend to do with the land?
Fight to keep it at all costs, and use their ownership of it to gain a voice in any future public inquiries into the building plans of BAA, which operates Heathrow. They also plan to divide up the one-acre plot and sell pieces on to climate change activists all over the world. Technically, if BAA is given the all-clear to build a third runway, it would have powers to buy up the land using compulsory purchase orders. But don't imagine for a second that Greenpeace and its supporters will give up the deeds without a fight. The new tactic also signals the next stage in the fight to stop a runway being built. Those opposed to the plans are already thinking ahead to the lengthy planning and inquiry process that will take place should the Government give the nod to the project.
What are the concerns of the opponents?
The key concern for the green lobby is that a third runway would see the number of flights rise by 220,000 a year, making Heathrow the biggest single source of greenhouse gas emissions in Britain. That would make it very difficult for the Government to meet its promise of reducing carbon emissions by 80 per cent by 2050. It has said the third runway will not go ahead if environmental concerns are not met. Protesters say Heathrow already breaks future EU limits on emissions with just two runways.
Are there any other obstacles to expansion?
There are other more pressing problems for the Government to navigate in the short term. It supports the construction of a third runway in principle. But although its final decision was widely expected this week, opposition from within Gordon Brown's own party may well delay any announcement until next week or later this month. Four Labour MPs have been promised a meeting with Mr Brown to discuss their concerns and have asked for assurances that it will come before any announcement is made over the future of Heathrow. Martin Salter, Andrew Slaughter, Paul Flynn and Martin Linton all challenged the Prime Minister during a meeting of Labour MPs on Monday evening. There are also murmurs of disquiet in the Cabinet, with Hilary Benn and Ed Miliband voicing concerns in private about the environmental impact of the project.
Is there any other opposition?
There is vehement opposition from local councils, which have formed the 2M group to fight expansion. And residents in west London have also formed a well-organised campaign. They are already organising a "flash mob" invasion of Heathrow's Terminal 5. And spare a thought for the village of Sipson, which would be swallowed up by a third runway. About 700 homes would go, signalling the end for a village that has been around for nearly 900 years. Bryan Sobey, leading the residents' fight in Sipson, said momentum was on their side. "I think the Government would give up this plan if it could, but it does not want to lose face," he said. "We have had huge media interest already." Both the Conservatives and Liberal Democrats are opposed to expansion, but want the Government to make a final decision. The Tories' transport spokeswoman Theresa Villiers accused Mr Brown of "dithering over the decision on Heathrow he has been promising for months".
Who is supporting a third runway?
British Airways, which has the prime take-off slots at Heathrow, is leading the charge in support of a new runway. The pro-lobby group Future Heathrow, made up of businesses and trade unions, placed adverts in national newspapers this week to make the economic case for expansion. It argues that, if Heathrow is not expanded, Britain will lose out as companies opt to do business in France, the Netherlands or Germany. The Unite and GMB unions are backing an expansion of the airport, which could create 65,000 new jobs.
Is it likely to go ahead?
Despite the delays – a decision had been expected before the end of last year – Mr Brown is expected to give the go-ahead for the third runway. The Transport Secretary Geoff Hoon is a supporter of the project, as is the Business Secretary Lord Mandelson. The delays are partly a ploy by Mr Brown and Mr Hoon to show they are taking objections to expansion very seriously – the official line for delaying a decision until January was to take full account of the 70,000 responses to the consultation on Heathrow expansion received by the Department for Transport. But the level of opposition is having an effect on government policy. Any announcement about enlarging Heathrow will be made as part of a broader transport package. Lord Adonis, the Transport minister, is keen on the idea of linking a new north-south high-speed rail hub to Heathrow, which could be used to sweeten the deal for environmentalists. The Government will also weave the construction of a third runway into its current rhetoric of wanting to create jobs and boost spending on Britain's infrastructure.
So will formal support from the Government be the end to it?
No chance. John Stewart, who runs the HACAN campaign group opposing expansion, said that when the Prime Minister gives the green light to the third runway, it will be "just the beginning" of a long battle to stop it happening. That is certainly true. Once the Government gives its backing, BAA then has to receive planning permission and navigate a public inquiry. That will take years and public opposition will be both noisy and widespread. If the Conservatives win an election in the meantime, they have vowed to rip up the plans for expansion. They have consulted lawyers on the issue and believe they would have the power to tear up contracts. The party may even have time before a public inquiry is completed to change government policy to stop the building work from starting.
How about a Thames estuary airport instead?
Several feasibility studies have been set up into the possibility of "retiring" Heathrow in favour of a new airport in the Thames Gateway region, which would spare any residents from enduring noise. But the studies have rejected the idea as unaffordable. It may not satisfy green campaigners, either – it is just another runway, after all. But the Mayor of London, Boris Johnson, is a fan and has commissioned another study into his own plans for an airport near the Thames estuary. In the meantime, he has become another heavyweight opponent of Heathrow expansion.
Should the protesters be allowed to stop Heathrow's development for good?
* The increase in noise and pollution created by more aircraft will have dire consequences for residents on Heathrow's flight path
* Expanding Britain's airport infrastructure will make it impossible for us to fight climate change effectively
* If the Conservatives win the next election, they say they will tear up construction contracts in any case
* The plans may create as many as 65,000 jobs – good news at a time of plummeting employment figures
* Without a third runway, the British economy will lose out to countries with larger hub airports
* The scheme is part of a broader transport package including a high-speed rail link designed to get Britain moving