I am not altogether sure why the editor keeps sending me books to review on filth, stench and defecation. I don’t think I have any greater interest in these subjects than is normal. Nevertheless, it must be said that this latest offering, a survey of worldwide lavatorial habits, is strangely fascinating. The Big Necessity is shit from beginning to end – but not in a bad way. In fact, Rose George’s bold claim is that ‘shit doesn’t have to be – and shouldn’t be – a dirty word’.

She wishes not only to describe the world, but to change it. (She has written for The Guardian.) Many of the facts she adduces certainly suggest that something needs to be done. Poor sanitation in developing countries means that people there may ingest as much as ten grams of faecal