Anew book from Philip Ball is always an eagerly anticipated event, but this one exceeds expectations. This is partly because his writing reaches ever higher standards, but also because the passage of time now makes it possible to take a dispassionate view of his subject matter: the behaviour of scientists in Hitler’s Germany. Were they ideological Nazis, active supporters of the regime? Or self-serving cowards, out to save their own skin? Or something in between?

The answer, of course, is the third option; but Ball’s triumph is to tease out the shades of grey and leave us with some sympathy for even the most deluded, while elevating our appreciation of some of those who were perhaps less cowardly than certain historians have suggested. His focus