Diana Cooper, author of the letters in this book, was born to privilege. She was the youngest daughter of the eighth duke of Rutland. She was a startling beauty who, from the time she was presented to the court in 1911, was the darling of society and the gossip columnists. Her marriage to Duff Cooper was something of a sensation as he was a penniless commoner. For his gallantry in the First World War, Duff Cooper was recommended for the Victoria Cross but was eventually awarded the Distinguished Service Order. He joined the Foreign Office and held many important posts during the Second World War and its aftermath. He was a made a peer, Lord Norwich.

The letters are all written to their son, John Julius Norwich, when he was growing up. Norwich now sits in the House of Lords and is a well-known writer and broadcaster. His histories of Venice, of the Byzantine Empire and the Popes are extraordinarily well-written and well-researched. He has lovingly brought these letters together and has edited them with a remarkable light touch.

Norwich informs his readers that his mother was an inveterate and an unstoppable letter-writer. It is best to quote Norwich on how his mother cultivated the art of letter-writing: “I can see her now, sitting bolt upright in bed, cross-legged, a pad of paper balanced on her right knee, a pencil in her hand — always pencil, so as not to get ink on the sheets. Bed was the bridge, the control tower, the centre of operations. On it was the telephone, the writing paper, the addresses, the engagements. Never did I see her sitting at a desk or other table if bed was within range. She always maintained that she could never keep a diary; it was no fun writing to herself. So she wrote to other people instead — to my father if he was away somewhere, to her old friend Conrad Russell, or to me, her son. And she told us everything that happened, writing in a style that was entirely her own — there was no way that any letter of hers could be mistaken for anyone else’s. The writing was effortless; an hour would produce five or six long pages; then she would fold them roughly, give the envelope a quick lick, address it — still in pencil — and as often as not, start on another.’’

These letters cover an important period in the history of England and Europe. They begin just before the Second World War when their recipient was only ten years old. They end when Norwich is 23, married and about to enter the Foreign Service. She wrote to him after that only when he was posted abroad.

The letters are detailed but never dull. They are full of fun. Writing immediately after her husband was offered a peerage, she commented: “I’m so tired of being congratulated on my big step down.’’ The step down is explained by her son. She was by birth Lady Diana Cooper, a title that she enjoyed in her own right. The inclusion of the Christian name denoted that she was a duke’s daughter. From having a title in her own right, she became Lady Norwich, a lord’s wife.

The vast dramatis personae flitting through these letters, often referred to by their nicknames, are all identified and explained in the footnotes and also at the end of the book. What is charming is that in the editing and the brief commentaries there is no attempt to conceal anything. How many sons will have the courage to say that his mother was actually the child of a long and passionate affair between the duchess of Rutland and Harry Cust from a neighbouring estate? Or to write that his mother had had a couple of light-hearted affairs and his father many? But Diana and Duff Cooper were devoted to each other. John Julius is their proud son.