In Sex, we unearth remarkable evidence of the complex passions of medieval men and women.

On the one hand, there was a down-to-earth approach you might expect in a peasant society; on the other was an obsessive abhorrence of desire grounded in religious fervour. Professor Robert Bartlett explores the subject using medieval sources, and quotes some of the questions the 11th century Church recommended priests to ask their parishioners: "Have you committed fornication with your step-mother, your sister-in-law, your son’s fiancée, your mother?"

Medieval knowledge about sexual difference was rudimentary and governed by a misogyny rooted in the Bible. Eve was the cause of original sin for tempting Adam in the Garden of Eden. An early church father had this to say to women: "The curse God pronounced on your sex weighs still upon the world. You are guilty – you must bear its hardships. You are the Devil’s gateway".

The Church preached hatred of the flesh and promoted the cult of virginity. Robert tells of the compelling story of Christina of Markyate who defied her parents and her husband to maintain her chastity.

And yet it was the medieval world that gave birth to the modern concept of romantic love. 12th century troubadours began to sing songs of love to women who were to be adored. For the upper classes at least, the rules of love were reinvented in lengthy treatises, the heroes and heroines of love celebrated in poems: Lancelot and Guinevere, Tristan and Iseult.

Robert tells the tragic story of the real life lovers Abelard and Héloise – Abelard the great scholar, Héloise the niece of a canon at the Cathedral of Notre Dame. Their love letters from the 12th century are astonishing in their frankness, passion and willingness to break conventions.