Fairdealfrank 
This is a paper airport, proposed so as to make it look as if Johnson is doing something and to promote his desire to PM. But no one is doing anything.
The simplest two points are:
- There is no money.
- The HS2 is designed to help quite a lot of people through an (eventually) long route. BUT that is being held back by a few MPs trying to save their seats as their voters don't want it.
How many voters/MPs are going to protest at:
- such a major amount of rail + road + airport building across multiple areas
- disruption in local areas during building
- many properties (domestic and commercial) dropping rapidly in value when the move is made
- the 'M4' corridor is what it is BECAUSE it has London and LHR on it. If LHR goes - then the 50 years of investment in the corridor loses value
- BUT if LHR does not close - then how can you support two major airports, supposedly doing the same thing.
Never going to happen - even after Boris is PM sometime after 2020.