SS,
You really can't compare the financing of a motorway with a new airport almost a century later. They are totally different kettles of fish.
The closest motorway comparison would be the M6 Toll, but even this has a different metric.
So please let me know your own thoughts on:
1) How the business plan would pay (consequential benefits aren't relevant to investors, just hard cash)
2) How this new united Europe will evolve, when everything now looks like disintegrating.
3) Why this plan would be Marvellous, not Mirabel.
4) Which London airports would close, and how they would be compensated?
5) Which airlines, high or low cost, have expressed the slightest interest inthe proposal?