Government White Paper 2003.
My italics;
11.62
The Government supports a third runway..............once we can be confident that the key condition relating to air quality can be met. We judge that there is a substatially better prospect of achieving this with a third runway and terminal capacity built in the 2015 - 2020 period, as long as we take action without delay to tackle the NO2 problem. The Government's support would also be conditional on measures to prevent deterioration of the noise climate and improve public transport access as set out above.
And they wonder why no-one believes a word they say.