Women very rarely make promises at the start of a lover affair. In fact it is men who say 'We'll always be friends' or who swear eternal love. Why is this? Starting with the motif of the promise, by way of the Brontes, Four Weddings and a Funeral, Daphne du Maurier, Nick Leeson and Elizabeth I, psychoanalyst Darian Leader explores the essential questions about love, sex and fidelity.