A head of steam is growing behind calls for a third runway at Heathrow. At least that is what a conjunction of powerful interests is trying to suggest. Not a day currently passes without someone challenging the Prime Minister to renege on his party's manifesto commitment giving the go-ahead for that runway, or hinting that he has already changed his mind.

Yesterday, it was the MP Tim Yeo, chairman of the Commons Energy and Climate Change Committee, who asked David Cameron whether he was "man or mouse" – the "man", in his book, being brave enough to reverse tracks in order to stem Britain's otherwise inevitable decline. But it could have been the director-general of the CBI, John Cridland, who believes the UK is losing business to continental airports that have more direct connections to more Chinese cities, or Len McCluskey, of the trade union Unite, for whom a third runway means jobs – both of whom were quoted by Mr Yeo. Or it could have been Willie Walsh, head of British Airways, who still hankers after that runway, while officially accepting that the prospect is dead.

The purpose of all this would appear to be to make the third runway a fact of life, so that any controversy, when the U-turn comes, is minimal. So far, though, the Government is sticking to its manifesto – or so the Transport Secretary, Justine Greening, said yesterday, citing the Coalition Agreement as cover. Then again, she has her own vested interest: her south-west London constituency, where aircraft noise is a central issue. This may be why there has been speculation that she could be moved in the expected Cabinet reshuffle.

But key elements are being lost in all the positioning. One is the voice of those whose lives would be affected for the worse by a third runway and who believed they had won the battle. Another concerns carbon emissions and damage to the environment. And a third is any semblance of transparency in government decision making. It is not certain that more capacity is needed and there are other options, including more intensive runway use at Heathrow, expansion at Gatwick, or a completely new hub, to be weighed. Whatever case there is to make must be made openly and argued out in public. The closet lobbying must stop.