The classic visual PowerPoint cliche to indicate inspiration is to draw a light bulb over someone’s head. Physicist David Mackay’s inspired idea was that the humble light bulb would provide a graphic way of communicating to non-physicists the scale of the energy gap now facing our society.

We asked David to be the external assessor for our new Open University course on Energy Measurements at Home partly on the basis of his terrific book Sustainable Energy — without the hot air. But we had no idea then that he would be appointed Chief Scientific Advisor to the Department of Energy and Climate Change. It’s clear that he made the video before he knew it either. Wonder how his political masters are getting on with such a clear thinker — and speaker. I suspect they are finding it, well, slightly uncomfortable. Speaking truth to power is generally not appreciated, and I can’t see Professor Mackay trimming to the wind. Someone once accused him of being against wind turbines. He replied: “I’m not against anything. But I am for arithmetic.”