Most people think of Voltaire as a toothless old man in a rage. In what many critics regard as Nancy Mitford’s most successful essay in history, we see him when he was young, fashionable and a lover. His mistress, the Marquise de Châtelet, known as the divine Emilie, was a society woman and also a physicist of importance; she translated Newton and popularised Leibnitz. But she was no dreary blue-stocking; she liked parties, gambling, clothes, jewels, and making love. When they fell in love, she took Voltaire to live at Cirey, her husband’s home in remote Champagne. The Marquis preferred wars to his wife’s intellectual conversation and she and Voltaire, during a five-year honeymoon, carried out most of Newton’s experiments. But after eleven years Voltaire, asserting untruthfully that he was too old to make love, left Emilie for his niece, Mme Denis. Emilie in turn embarked on an affair with the Marquis de Saint-Lambert and all went merrily, with Voltaire, du Châtelet and Saint-Lambert on the best of terms until, at the age of forty-four, Emilie became pregnant. The manoeuvres to persuade du Châtelet that he was the father provide an uproarious chapter in this amusing book. Alas, it ended in tragedy, to the great despair of the divine Emilie’s husband, two lovers and all her friends.