Nigel,
However if its a 4 runway LHR or new hub north west of LHR then that's too close for comfort..luckily can see the arguments lasting another decade before they choose.
Fortunately with the UK's arcane planning system, vociferous NIMBY lobby, and constant political indecision, I reckon that oil will have run out before LHR ever got 4 runways!
Even HS2 will get done before LHR get's it's forth runway, possible even their third.