Taken from a rational economic perspective, the picture of this additional runway for Heathrow looks sharp and sensible and is widely supported by business as the right choice. If it ended there we could be confident that the project will proceed. It does not end there. It starts there, so where does it end? The odds are on nowhere.
The political , environmental and legal challenges are likely to bog it down. There are at least a million people whose lives will be changed by noise and pollution at unacceptable, even illegal, levels. Tory voting constituencies which are affected and feel betrayed by promises previously made, vital to the re-election of May’s government, are up in arms. One MP has resigned. The Liberal Democrats are looking forward to a comeback. They do comebacks rather well. So although it may have been the right decision in theory, it was almost certainly wrong in practice.
A better way would have been to sanction new runways at Gatwick, Luton and Standsted, built by private investment, and for the government to build a high speed rail line, to link all four London airports, Heathrow, Gatwick, Luton and Stansted, to each other and to the main HS rail network. That would have really shown the world that Britain is open for business.