Oliver Letwin: Nigel can't know whether there is going to be a successor to Kyoto.

Nigel Lawson: Well, look, there'll be an international agreement in the sense that there will be platitudes. The acid test is: will there be an agreement to have binding cutbacks for all participants on their carbon emissions? Instead of arguing about it, we could have a wager on it.

Oliver Lewtin: I'd be very happy to have a wager, and I offer you a £100 bet that before either of us is dead, whichever is the first - our estates can pay - we will see a very substantial agreement on carbon reduction.

Nigel Lawson: But I don't think I want the bet to be "in my lifetime" because I'd like to get the £100. I'm sorry it's such a modest amount you're prepared to wager — it shows how unconfident you are — but I would like to be able to collect before I die. So I think we should say "by the time Kyoto runs out", because there is meant to be no hiatus; there is meant to be a successor to Kyoto. So "by 2012 we will have the agreement" — maybe I'll die before then, of course -but 2012 is the acid test.

Oliver Letwin: On the same basis, Nigel, I'm perfectly willing to take that bet too. The reason I'm willing to take the bet is that I know that the only way it can be made to happen is if we try to make it happen and if we build up the moral authority to make it happen by taking the steps ourselves.