Ireally can’t believe it is necessary to say this again. But oh well, here goes. At the beginning of my first ever school lesson in economics, my teacher informed us that before he could continue, he needed to introduce us to the most important economics professor we would ever encounter. And then he wrote on the board: TANSTAAFL.

Tanstaafl, he explained, stood for “there ain’t no such thing as a free lunch”. And for all I went on to learn later at school and then at the London School of Economics, nothing ever provided greater insight than these first five minutes. The whole of economics, all the textbooks and lectures, is basically a footnote to this central idea. Things have to be, and always are