I read with gloom the arguments made against expansion at both airports.
“Increase in CO2 levels…” – cars produce 100 times more Co2 but no mention them.
“Increase in noise levels…” – rubbish, because the level of noise has been reducing gradually since the 1970s. Now, the newer and newer generations are producing less and less noise.
“Other airports can absorb any increases in traffic…” – that is precisely why Vietnam Airlines is transfering from Gatwick to Heathrow. Distance from the final destination is vitally important. Anywhere more than 50kms from London is a non-starter. Anywhere east of London is too far away for the vast majority. The only remaining alternative is Luton which is possible but only with massive investment and only when targeted as an, eventual, four runway option.
With your permission, some more of my thoughts on the matter.