I think all will agree that Heathrow is pretty much full - at least until a new runway is built. Unless LHR's major carriers deploy large numbers of widebodies on European shorthaul, the number of pax passing through LHR is not going to grow significantly before 2020
Therefore, encourage the air travel market to deploy some more capacity to UK regional airports. Connectivity to the world helps trade and improves the UK economy. Perhaps people travelling from Oxford to Munich could be encourahed to use Birmingham rather than Heathrow, saving Heathrow space for someone in London for whom Birmingham is a non starter ?
This idea is all about introducing a greater degree of economic price rationing so that space at Heathrow is used by those who value it most. If Heathrow had R3 this idea would never have been published