It’s the smell that hits you first: a ureic stench so thick it feels like something solid is foraging up your nostrils. Tourists are given sprigs of mint or rosemary, like the nosegays carried by Renaissance gentlefolk. But if you want to be accepted by the tanners, you have to go unprotected. I’m turning up for my first day as an apprentice tanner, in the old city of Fez, with nothing to filter out the odours.