Come on, how much do you make? Do you make ₤60,000 a year? Do you? Do you?” The prisoner is insistent, but he is trying to make a point. John (not his real name) is serving a three-month sentence at High Down prison just outside Sutton, south London, for an elaborate form of shoplifting: buying expensive goods, taking them home, going back to the shop with the receipt, picking identical items off the shelves and taking them to the customer service desk for a refund.

His point is that the roughly ₤60,000 a year he makes is more than he could earn from a legitimate occupation. A spell in prison is just an occupational hazard, he says; you rarely get caught, and if you do, the sentence is short.