Silver,
I was no fan of Blair either (and yes, got to confront him too), but it is just silly to say that all he cared about was being PC - he left that to Harriet Harperson!
A thread about infrastructure has to dip into politics, but it is completely ridiculous to say you should cut back on other government spending to build a new airport, which (a) could easily be billions of pounds over budget if publicly funded, and (b) could also still suck money out of the economy if it enables more flights to be taken to holiday destinations.
Now there are probably some figures out there that say that LHR & LCY provide a net gain to the economy through enabling trade and exporting specialised knowledge based services, but I doubt that could be said of any other airport.
So think again about what you would want achieved with this new airport.
a) Who would pay for it?
b) How would you ensure that it did indeed focus on the kind of flights that helped the economy, and that it didn't just add extra general capacity by taking the pressure off LGW, STN etc?
I note that point (b) is actually very difficult to do, unless you were to develop a routes committee which decided which destinations should and shouldn't be served. Silly of course, but without that, you have little evidence that your sinking sands airport could generate any kind of ROI for the nation as a whole, let alone its shareholders, whether institutional, private or government.