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.
+
A new out of town airport will be built, eventually.
Whilst I'm doubtful that the former will go on for ever (fuel costs, taxes, environmental concerns and so on), even if we do have growth to the tune of, say, +50% on current London capacity - 70m pax pa, this can still be met by the other airports in the London area. Whilst this isn't the perfect solution in terms of hubbing, it is still a solution and it is far more practical - just doesn't appeal to the big ego types, hence:
Your tally of new airports wheere the old one did not close is MOST instructive and a detailed explanation behind all of those should be compulsory reading for Boris. But, since he doesn't care if the airport is built, he does not have to read anything!
Say what you like about Boris and his preference for big books with pictures in them over detailed technical documents (loads of us are like that too!). Are you really saying you don't think Boris cares less whether it gets built or not? Surely the first thing politicians look for when they reach high office is something that will give them a legacy. What bigger legacy than Boris Island Margaret Thatcher Intercontinental Airport - after all, one thing guaranteed is that
she will be dead by then!