Gatwick obviously for a 2nd runway, + airporters?

An imaginative campaign is being run by Gatwick to make sure another runway goes there

but Heathrow is also arguing for an additional runway, built perhaps above the M4.

Which airport should be chosen?  Certainly there is more space at Gatwick and the rail connections are good, although the Crossrail project will eventually include Heathrow.  Any additional runways will need fast interconnection to all transport hubs.

And that's where airporters come in.  Their speed around an airport site, or between airports interconnects them into one hub, so it doesn't really matter where the runways are.  It is an idea assumed in my second Buffalo Future novel.