If you had to choose an energy policy for the 21st century, would you prefer a system based on “contracts for difference”, with a single-party counterparty, a levy control framework and a capacity market? Or would you go for “premium feed in tariffs”, with an appropriate tariff degression mechanism and a strategic reserve?

Not sure? Neither are a lot of energy ministers on their first day in the job. So think of their relief when they come across someone like Dieter Helm. This extensively published Oxford professor of energy policy is an economist with firm ideas about how to design an affordable, climate friendly electricity sector that he can readily explain in plain English.

That is one reason why Prof Helm’s advice has been sought over the years by every institution from the European Commission to the Polish and British governments, and the occasional investment fund. Lately, he has turned his agile mind to one of the great problems of our age: why the world’s efforts to curb the carbon dioxide emissions behind global warming have gone so wrong, and how it can do better.