A man in his late fifties wearing battered jeans and a bush jacket with pockets stuffed full of fossils stands at a lectern. "How can hydrogen gas become a fish, develop flippers, jump out of the water and become Tony Blair?"

He has beat-perfect comic timing, and there are gales of laughter from the audience. He flashes a picture of a T-rex on his overhead projector. "Some evolutionists say that frogs developed legs to outrun dinosaurs. You may ponder how quickly you'd need to evolve legs if you were chased by one of these."