Documentary is a slippery genre to define; classifications can be out of date before the printers’ ink has dried. Acceptable documentary practice depends on a subtle three-sided process of negotiation. On one side are the habits and beliefs of audiences, what viewers will put up with or believe in. On another are the demands of cinema and television as media, how the film or programme will fit with current practices and expectations. On the third are the aspirations of film-makers and participants, cynical or idealistic, motivated to show, but also to hide.