I want to deal with a pseudodox before I give way to my hon. Friend.
It is important to recognise that air quality has improved. I do not want there to be any misunderstanding about that. Over time, air quality in this country has improved. That goes right back to the clean air Acts of the late 1950s and through the 1960s. Even in recent years, air quality has improved with respect to nitrogen monoxide emissions by something like 20%, so let us not start from a series of misassumptions.