I suspect I'm like many people, I of course tried to change my behaviour, when I travel up to my constituency in Sheffield and back again every week, I almost always do that by train, unless there is so much clobber with the kids that I simply can't carry it on the train. But I don't do enough. I'm acutely aware I don't do enough, I'm like many, many people, I wish I could and would do more. Part of the problem, because you referred specifically, Nicola, to aeroplanes, and you're quite right that flights at least when they are able to fly, and there isn't too much volcanic ash around, do create a growing proportion of the CO2 emissions, so we need to tackle it. I think what is irrational is the moment you have a tax system which taxes passengers in aeroplanes, that means that planes with freight in them, for instance, aren't taxed, to reflect the pollution they cause. You've got lots of planes that are half empty or barely got any passengers at all. If you changed it to a plane tax, you would make a dramatic difference in cutting down on unnecessary aviation pollution.

Hold your horses. You've asked... Gordon Brown asked me about nuclear power. I don't have a theological opposition to nuclear power. I just think it's extraordinarily expensive, very, very expensive indeed. There are some calculations that it would lead to average energy bills increasing in this country rather than decreasing. It takes a long, long, long time to build these nuclear plants. All the experts agree that it would take well into the next decade to create new nuclear energy, which would be too late to deal with the energy problems we have now. For a fraction of the money that I think both David Cameron and Gordon Brown want to spend on subsidising the nuclear industry, we could develop mass insulation programmes of our homes, our schools and our hospitals. Remember, 27% of all carbon dioxide emissions in this country go straight out of your window, through the roof of your house. If we only used energy more efficiently and also, of course, invested some of the money which would be wasted on big nuclear projects on wind energy and other renewable energies, I think that is the way towards a sustainable future.