Just a quick note on the Davies Review.
I don’t think the NW of Heathrow option has much legs. It involves demolishing the whole of Harmondsworth including the conservation area and the Grade I listed Great Barn, as well as putting Sipson at the end of the runway. You might as well demolish it completely.
The option requires building over or diverting the M25.
The other Heathrow option is to extend the northern runway to enable it to be split into two take off and landing runways. This option is half of the ‘Heathrow Hub’ proposal not any consortium but a group of friends led by a former Concorde pilot. Their proposal would include a transport hub to the north. It also involves building over the M25.
This has all of the advantages of the idea of shifting many flights to the West but with fewer disadvantages. There would be a big noise footprint plus which I’m not sure Zac Goldmsith, Hacan etc. either full appreciate or being so disillusioned by being let down so many times before are prepared to accept. I cant see any point though in adopting half the Heathrow hub idea, if there is a ‘nouse plus’ then why not develop four runways even if they are not at full capacity. There would be major gains in fewer flights delays that result from Heathrow’s 99% capacity at present. The idea seems to be that runways are a ‘bad’ which you should provide as late as possible to minimize the harm This isn’t necessarily the case with the hub proposal however, as you can increase runway alternation.
The big downer is likely to be how practical it is to keep the existing runways and M25 ‘on track’ whilst you extend the airport. The sharpness of the bends of the diverted M25 in their drawings looks impractically sharp and dangerous. It would be more practical I think to dig a tunnel under Heathrow to the east slightly, then divert traffic, then extend the new runways to the West.