Silver, with reference to the compulsory purchase of LHR, it's not “the wrong way around“. You imply that Ferrovial would willingly sell LHR or that it could be nationalised by the government in order just to close it.
You also state that “it is the purchase and sale of LHR as an industrial/residential site that would pay for Silver-Boris“ but do not explain (1) the mechanics and timing of transferring money from the owners of Silver Island to Ferrovial, (2) why on earth Ferrovial would accept it (it could never be enough!), and (3) how the Silver Island owners would have so much money sloshing around despite the expense of building the airport, and having no substantial income until the airport is up and running and successful.
To assume that it will all be funded by the government is fantasy. Your premise that Silvering Sands requires the closure of LHR to be successful is probably correct. That is the main reason it will never happen.
It just does not add up.
Jabird, good point about Sempang. It illustrates well that growth in civil aviation is always underestimated by governments, and has been for a long time, and not just in the UK.
BA, VS, but regrettably not BD would indeed face huge costs to move out of LHR, so why would they? As airports and airlines are privately owned businesses they will make decisions that favour their passengers and therefore their shareholders. Not surprisingly, that means staying put.
Ferrovial, also a private company, will also have shareholders’ interests at heart, and would move heaven and earth to ensure that airlines stay at LHR. The presence or possibility of Silver Island could, ironically, make LHR even more attractive to airlines!
Paxboy, think that the 480,000 ceiling was set years ago, perhaps back in the 1960s. Suspect that at the time, short-sighted functionaries never considered that the limit would ever be reached!
This was the time of the government’s ludicrous and damaging “second force” aviation policy, which was intended to promote growth at LGW at the expense of LHR, by building up LGW as a hub for a private UK airline.
Perhaps the “second force” policy was a forerunner of the JFK/EWR dual hub that works well in New York today, because of the availability of a continent's worth of domestic connectivity. Back in the UK, a succession of airlines were based at LGW: BUA, BCal, Laker, VS, etc.. VS only survived because it was able to move its hub to LHR. As a result of this policy, there was inadequate expansion at LHR when it was needed and led to the situation we find ourself in today.
At this time the “flag carrier” airlines, BEA and BOAC, and most major airports were government-owned, so they could dictate the base airports for each British carrier and the destinations they could fly to. Business and economics did not come into it at a time when fares were the same on all airlines and fixed by IATA. It was simple: first class fares were double those in ecomony. For example, South America and West Africa destinations were "given" to BUA ex LGW. BOAC ex-LHR was excluded from those routes.
Agree 100% with your comments about Boris, particularly the last sentence!