On an August evening in 1928 May Donoghue, a shop assistant, entered a cafe in Paisley. The circumstances of her visit made legal history. A ginger beer was ordered for Mrs Donoghue who famously complained that, to her surprise and shock, a decomposed snail had tumbled from the bottle into her glass. Mrs Donoghue sued for the nervous shock she claimed to have suffered as a result. The question whether she had a case in law against the manufacturer of the ginger beer was argued as far as the House of Lords. It is hard to overstate the importance of the decision in Donoghue v Stevenson. It...