I dont get this shutting down Heathrow business in order to justify/finance/build a Thames estuary new four runway megahub? Why not leave Heathrow alone but reduce the throughput a tad whilst still having your four runway euro megahub in the Thames Estuary? If it's mainly for interlining for other international flights, let it focus on that, whilst Heathrow can be left for those wanting to get off and come into blighty. It just seems utterly insane to close down Heathrow - have both. Heathrow may be grim, but why on earth would you just stop using it when it has so much infrastructure that would be extraordinarily difficult to utilise/convert into anything else but an airport - absalutely insane to contemplate it becoming any kind of industrial park - what planet are they on?
In the meantime, although they're scattered about a bit, there still is quite a lot of runway capacity unused all over the southeast - Biggin, Manston, Lydd, Oxford, Cambridge, Farnborough, Southend for starters - several hundred thousand additional unused movements permissable amongst that lot. A bit of Government support and they can all persue their commercial dreams without the bucket load of red tape in the planning system.
Then you have the woefully underutilised RAF Northolt WHICH IS HEATHROW'S THIRD RUNWAY!
Then you have a raft of used and unused military sites such as Brize, Benson, Upper Heyford etc.