Recently I was invited to a large, televised debate about how we should deal with climate change. The circumstances were spectacularly intimidating, with Tory grandees Nigel Lawson and John Redwood poised to respond to my remarks. (Despite my nerves, I resisted the temptation to follow the old public-speaking advice and imagine my fellow panellists naked.) I was the first to speak, so stood up and I talked about the cappuccino I’d bought that morning.

The curious thing about the cappuccino, I observed, is what a remarkably complicated product it is. The milk came from a methane-producing dairy herd, probably somewhere in the UK but perhaps further afield. Behind the scenes stood the farmers, the cattle breeders, the manufacturers of refrigerated tanker trucks and countless unknown others. The coffee was steamed out of Brazilian beans using a machine of Italian manufacture. The machine was electric, although whether the electricity came from coal or gas or tidal power I have no idea. The complexities are endless. (This whole tale is the kind of story economists like to tell each other, originating – I believe – in “I, Pencil”, a 1958 essay by Leonard Read.)