Surely runway capacity isn't the most significant issue regarding London Airport's congestion?
Every time I've been into the place (as a passenger), I vow never to use it again. Arrival often includes several minutes observing the Essx countryside whilst stacked in the hold. Then a lengthy taxy; even if the processing time through customs and immigration is swift (unlikely), there's often a loooong wait for luggage and then 20 minutes of traffic jams in the Long Term car park bus before I can finally escape.
So any additional runway capacity is only going to make things worse.
Better use of regional airports should be considered first.
LHR usage is 'red car theory'. "Why do we make red cars?" "Because people buy them!" "Why do people buy them?" "Because we make them!" - which translates into "Why do people use LHR?" "Because that's where the airlines fly from!" "Why do airlines fly from LHR?" "Because that's where passngers fly from!"......
