When I said to my party we had to get real about the environment, and we to be a party that was a blue-green party, not just a blue party. I did actually once get a letter from someone couldn't really agree with this and said, Mr Cameron, if you're so concerned about carbon emissions why don't you just stop breathing? That was the moment I realised I still have some persuasion to do. In terms of my own life, the biggest thing we've done is to have proper insulation in our house and actually really can cut your energy bill and make life cheaper as well as greener. But I would say in the last six months, the biggest change, or the last year, the biggest change that I've been able to make is actually coming out very strongly against the third runway at Heathrow. I think it is wrong to do that. I think we should be going for high-speed rail instead. We should have a high-speed rail hub at Heathrow. Trying to make sure all the flights people take where you could take a train, it is possible to do that. I think it would be a really big step forward.

Of course we need an energy balance, and we need nuclear, we need renewables, we need the full range. It's a great opportunity for our country to do these things. I think one of the biggest opportunities we've got is actually with our own homes. We have a proposal called The Green Deal. We want to say to everyone in this country, that you can spend up to £6,500 on your home to insulate it and better protect it, and then you can see your energy bills come down. And we will have companies, Marks & Spencers and others have expressed an interest, to come and carry out that work and pay for it and share with you the reduction in the bills. I think that would show people that going green actually can save you money. It can actually get Britain working again, it can cut carbon emissions, it can cut fuel poverty. For all those reasons, I'd want it to be a really big part of the first Queen's Speech, if I'm elected as your Prime Minister.