Mark Purdey's life changed one day in 1984, when a Ministry of Agriculture inspector told him he must administer a toxic organophosphate pesticide to his dairy herd. Passionately committed to organic farming and convinced of the harmful effects of chemicals in the environment, he refused to comply. "It was as if my whole life became focused," he explained later. Before they had a chance to prosecute, Purdey took the Ministry to court and won his case. Those experiences led him to challenge the orthodox line on the origins of Mad Cow Disease and its human counterpart, variant CJD. Could the...