couldn't some of the 37% of passengers that are in transfer and don't need to be in London or the SE transit elsewhere?
"Getting rid of transfer passengers will ease capacity constraints" appears to be an increasingly popular argument, but none of its proponents have so far been able to explain how it would actually work.
If services exist from Heathrow to A and to B, how on earth will you prevent or dissuade passengers travelling from A to B from connecting over LHR?
Frog-march all arriving passengers off the airport premises with instructions that under no circumstances are they to attempt to continue their journey by air?