‘They deserve to be put away’; ‘Appeal the sentence – too short’; ‘They should lock him up and throw away the key’. How civilised has it ever been to imprison other humans – or to want to do it? How many prisoners had their fates determined by circumstance, how many by truly free will? How often has increasing prison building been used to increase a politician’s vote? How impossible would it be for most politicians to argue for fewer prisons because they do not work, when as a society we have to assume they do?

Modern experience in diverse countries – from Norway to the USA – may suggest that money can be better spent than on keys, bars and walls.