What is a poison and why are some things toxic? What sort of substances have criminals used, and how have poisoners been caught? Professor John Nicholson will answer these and other questions in the course of this lecture. His talk will include something about the chemistry of how poisons work, and of the substances that criminals have used. The talk will cover various cases, ranging from Dr Crippen (1910) to the Novichok poisoning in Salisbury two years ago. And the event comes with its own health warning: Be sure not to try any of this at home!