Picking up on the drift from LGW to LHR. Heathrow have known that LGW was to be sold and hence grabbed the premium traffic and developed the Loco business model.
BA were a willing partner in this as part of their future London Air Ways plan.
The public disorder that could follow a decision to go ahead with R3 would make Narita's conflict look like scuffle. No Govt will be willing to see injuries and deaths over the demolition of so many houses etc. On the other hand, a closely spaced parallel runway to the south of LGW affects relatively few homes. It's not too difficult to see the game plan, shurely?
SGC