Why poor comparison?
Seat 62K
Why is Mirabel a bad example? Does seem to have reasonable relevance to the current discussion. I remember using it just after it was opened.
How about Narita for another example. New airport, never fufilled it's potential while the airport it was designed to replace has recently been expanded.
"Moving" Heathrow would be the death of the high tech industries in the Thames corridor from Slough to Newbury. It is never going to happen.
As for extra capacity it is likely that we are never going to need it. Why? The price of oil will put an end to the need for Airport expansion, that's why.
There was a window of opportunity to replace Heathrow 30 years ago and it was lost. It will never be resurrected. Despite the confused mutterings of a deranged blond twit. Boy, but the people of London are going to reap what they sowed there!
Boris can't even find the money to fund Crossrail how can he fund an airport that NEEDS new transport links to make it work, of which crossrail is only one?