Build second runway at Birmingham, run HS2 via Heathrow, and Birmingham is then probably nearer to Heathrow than Gatwick timewise.
Simples....and much less expensive than Boris Island.
Whether it's BHX, LGW, Northolt or wherever, I really don't buy the twin hubs + train concept - there will always be some pax doing this, esp with BA & Virgin having ops @ LGW, but it should be the exception, not the main. Where does this work well in practice? ICN + GMP?
On the other hand, two separate hubs, whilst not ideal, may be the most practical answer - and by this, I mean each handling their own onward connections. That does work in NYC, and to a lesser extent TYO.
I'm not sure that BA's short haul routes from LGW deliver that much into the market, but some of those routes could feed long haul if they were at LHR. The long haul leisure routes can also all be fed, as GLA-ANU isn't going to happen point to point.
A number of airlines are starting to show that they will accept routes into LGW, as they can't get LHR slots - as we've seen new routes to HAN, SGN, ICN, HKG, PEK etc. Eventually, as LGW added more capacity, it could keep drip feeding this demand, but this would be an odd way to expand an airport - basically any new routes which were overspill would go there, long established routes stay at LHR. Talk about sloppy seconds!
It also seems odd that, as the govt first proposed the utterly pointless Heathwick, and then Boris Island, there has been little response from any of the established airports suggesting one extra runway at either of them might do the trick.
I think STN & LTN could continue to take more loco traffic, the former with a new terminal. but the commercial case for a new runway there, based on Ryanair yields, would be very weak.
Remember though that all this talk of AMs, FRA, MAD etc 'catching up' on London is slightly misleading - all those airports have a fair chunk of loco traffic, LHR has almost none (TS, 4Y). The only real comparison is with Paris - still take off 5m for loco @CDG? - but CDG has room to expand, LHR doesn't it. CDG can feed through fast train links in 4 directions, spanning into Belgium, Lux, Switzerland etc and most of France, it will take 30 years for LHR or to develop such a network, and even if that was done, that just feeds more people into a crowded space. At least UK regional airports have much more established loco routes, compared to their French equivalents.
2019 will come and go long before any new runway at LGW could get built, but how would a new runway & terminal there attract airlines from LHR by choice, rather than overspill? Skyteam could work with Flybe to feed into LGW, and they'd have a lot more space than at T4, but it would need to be the deal of the century to bring them over - and how could that be done in a way which left enough profits to pay for all the new construction? Still, no villages or sweage farns to move @LGW. LGW would also need much better rail links, and again, BAA/FV would scream about infrastructure being built to subsidise the case for a competing airport (pot, kettle, black!).
I can't see how LHR could be forced to close either, it would be challenged in the high courts. Govt lawyers would argue it had to close in order to protect this new national asset (owned by the Chinese). BAA/FV lawyers would say 'y
ou can't compulsory purchase one business just to protect the future viability of another, larger, business'. That is called a monopoly!
So there's still no easy answers. But whether we call it Boris Island, Thames Airport, or even if we let Silver continue his ego trip and call it Silver Island - it is still no closer to being a viable proposition.
PS: Architects make very little from large construction projects - combined with the engineers, you are looking at about 10%. Building contractors stand to gain much more, if they get their sums right. But if I wanted to be on the take for this, you can bet that with so much emphasis on the rail links, combined with a planning agreement you can guarantee limits on-site parking, any vacant land within 20 miles of the new site, especially near a station, could turn into a nice little earner - but you'd be in for a hell of a long wait.