I don’t believe the decision has been made.
The Transport Select Committee really isn’t in a position to determine policy, and it would have been helpful for BT to at least have set that out in its piece on that Report (which I commented on in the link above).
What is needed is cross-party agreement (not just intra-Coalition agreement) on a solution, or it won’t get through, which is why it has to be delayed until after the next Election. Labour did nothing on this from 1997 to 2010, and deserves the opprobrium for its usual stance of doing nothing during the good years and leaving others to sort the mess out as things get critical, and then sitting by the wayside complaining and throwing brickbats wherever possible.
What is agreed is that a four-runway solution is best. Where it is sited is anyone’s guess; there are many existing vested interests busy lobbying for a maintenance of the status quo at LHR; the opportunities presented by Thames Hub are realisable, cost effective and very exciting.
A short Third Runway might have been a good solution a generation ago (and does seem to be supported by many of the retirees who post on this forum) but it is not the right solution for the next generation of business travellers.
I have a feeling the answer will be a another runway at Gatwick, another runway and terminal at Stansted with improved rail links to London and some APD reductions for regional airports to push marginal traffic away from Heathrow, and further consultation on the site for a Hub, which will be determined in about five years time, but will not be sited at Heathrow.
Once Crossrail opens in 2018, the argument that it is difficult to access an airport in the Estuary becomes increasingly untenable; the fundamental requirement of access from the West will already be in place.