If [Cameron] and his team at CCC, which invests in building green energy facilities to reduce greenhouse gas emissions, succeed they will, he says, 'show we can reduce emissions, and prove that money can be made from doing that'.
It sounds very grand, and this tall 44-year-old sometimes says things that sound overblown. But who doesn't when they're talking about the environment? At least he's honest. On the one hand, he says that he could change the world. On the other, he says: 'I have no interest in putting on a hair shirt. I don't want to be told I can't live well.'
Cameron's insight is that environmental damage is behavioural and the best way of changing behaviour is not by regulating people but by offering individuals the chance to win and lose through their own decisions.
'Stern is absolutely critical in terms of the necessary shift in consciousness in the upper echelons of political and business decision-making,' he says.
Excuses for inaction from politicians and businessmen exasperate him, as do those who say the UK produces only 2 per cent of global emissions, and that the developing world, particularly India and China, is not listening to Stern or anyone else. 'One persistent lie is that China and India are not part of Kyoto. They are, but their response is differentiated. They have hundreds of millions of people living on less than a dollar a day.'
He is haunted by the possibility of failure, but the fact that big money has arrived has given him confidence that he is no longer in the wilderness. He is not a boastful man, but does have an air of vindication about the compromises he has made to bring environmentalism and capitalism together.
As he puts it: 'The tree-huggers were right. We have to tip our hats to them and get on with the solution, which frankly we would not trust them to implement.'