When 100,000 angry residents affected by your plans aren't the strongest opposition you face, you probably need to reflect on what you are doing. That is the problem Gordon Brown is facing with plans to expand Heathrow to incorporate a third runway, which has been met with fierce opposition, even from his own cabinet.
Presenting a united front is crucial for all top-level decisions, so the prime minister must convince sceptical ministers like Harriet Harman and David Miliband his ideas are necessary for economic growth and do not contradict the 2008 climate change bill. Once he's done that, he can deal with rebel Labour MPs and the opposition, who've been very vocal in their outrage. But it won't be easy. The bill promises an 80 per cent reduction in carbon emissions by 2050, and aviation already accounts for 13 per cent of current levels.
Not only that, but the proposals could result in thousands being forced to leave their homes as an expanding Heathrow eats up nearly 1,000 homes in its path, along with schools and shops in the area. And that's not counting the 100,000 people who would suddenly find themselves living under the flight path of the new runway.
Andrew Slaughter, the Labour MP heading a delegation of rebels against the extension, has called for a re-examining of the 2003 white paper into the airport's expansion. Mr Slaughter told politics.co.uk: "Opposition to the government is very strong and diverse and is not restricted to London. We are deeply concerned about the thousands of people whose lives will be damaged by this unnecessary expansion which totally goes against the 2008 climate change bill." According to Mr Slaughter, the white paper is now seriously dated and needs re-examining because of the considerable political and climate changes since 2003.
Norman Baker the Liberal Democrat transport spokesman has branded the idea of expanding Heathrow as "totally wrong". He makes the same points as most other anti-expansion MPs, saying the idea goes completely against the government's desire to tackle climate change - particularly that 80 per cent emission reduction promise. Baker said: "It will be impossible for Britain to cut its carbon emissions by 80 per cent if the planned expansion goes ahead.
"This is totally wrong and completely goes against what was agreed and set out in the climate change bill this year," he added.
Labour MP David Taylor accused the government of not presenting the facts properly, and of ignoring more environmentally friendly alternatives. Taylor has called the economic arguments in support of expanding Heathrow "shaky" and based on questionable evidence. He has put forward rail investment as a viable alternative. The Conservatives have also backed this idea. Research by the National Union of Rail, Maritime and Transport Workers (RMT) has identified 100,000 of the 473,000 flights from Heathrow in 2006 were to destinations where viable rail links already exist. There would be enormous environmental benefits as well, with high speed rail emitting between eight and 11 times less CO2 than air travel.
The PM has much to do if he wants to push through the plans, starting with persuading dissidents within his cabinet. Once he's got through them, the Labour rebels, opposition parties and the communities affected by the new runway, he'll face up to his biggest problem. How do you reduce emissions by 80 per cent while increasing the number of flights into and out of the UK? Without a solid answer to that little quandary, the public might start to ask why anyone would promise things that just don't fit together.