I have made this point before but the only way of cutting through the political log jam is to announce the closure of LHR and its long term future as giant Tesco depot with 8000 artic lorries per day plus a new prison and sewage works for west London. Also relocating to the remote ends of the Thames estuary will mean that the influential but thoughtless people who live in Richmond Twickenham and Kew will no longer be anywhere near an airport so they cannot make day return business trips to the continent and have an 80 mile journey to the nearest airport.
So unemployment around LHR itself and collapse in property prices for miles around means people will be begging for another runway where Sipson now is and the folks there will move if they are given fair compensation. (unlikely i admit with government involvement)
Make it clear to people that while having a giant airport nearby hs its drawbacks it also has a huge amount of plus points
PB