Duff Cooper (1890–1964) is remembered today as the husband of Lady Diana Cooper. He was a Conservative politician and ambassador to Paris; he was also a writer and biographer, and he wrote an enchanting memoir called Old Men Forget, but he was always overshadowed by his glamorous and successful wife. These diaries are a revelation, especially for the light they shed on Duff and Diana’s remarkable marriage.

In 1915 Duff Cooper made a pact with Cynthia Asquith to start writing a diary and see who could keep it up the longest. Cynthia filled her book much quicker than Duff did. Hers turned into one of the great diaries of the First World War – the brilliant, self-aware memoir of a brittle society beauty whose world was torn apart by loss and grief. Duff’s diary is less detailed, less emotional, but equally riveting.

When the diary begins Duff is twenty-five and a Foreign Office clerk. Most of his male friends are away at the war, and he is bored with the day job, but his evenings are spent frantically partying with the gilded youth of the so-called Corrupt Coterie. Here are Bongy and