I’ve thought the debate has now moved on from 3rd runway to a 4th (or in theory say turning Gatwick from 1 to 3) as I think to play catch up and the length of time any will actually take to get done if only a 3rd runway at LHR was built by the time it was completed then a need for a 4th would be required (and then there would be the debate of short sightedness of past politicians). If Heathrow does grow it is only honest to the people of the area that if that is what is decided then they should make no bones about the fact it will grow to 4 as a minimum. Then people can make more long term plans about living in the area.
Not to say the debate can’t include a new airport as some advocate but the debate should be about 2 new runways at the same airport – or a new build 4 runway airport (or even 6?) and have some long term planning for once.
Also the wider debate is how we make the chosen airport more integrated with High Speed Rail, local rail, buses, roads and how we can keep environmental impacts to a minimum. Not everyone is thrilled by ever growing air travel and its effects on the environment.