Ohhh, thats fine then...lets have 30 flights a day to JFK, 15 a day to Australia, all from LHR, which requires a 3rd runway to be sustainable, and make the entire UK population travel to LHR for a long haul flight.
What percentage of LHR pax live north of Birmingham ?
There is no reason MAN, BHX, GLA could not handle these pax, maybe even enough of them that LHR would not need a 3rd runway.
All it takes is a big sign at LHR saying "AIRSPACE FULL" and a carrier to commit to the nation rather than just its capital.
Bring on the yield & "London is the center of the universe" argument again....