When did the Mitfords become immortal? Was it in 1981, when they saw their life stories sung on stage in front of them, at the premiere of the musical The Mitford Girls (a shallow pastiche that Debo dubbed ‘La Triviata’)? Certainly by 2005 they were such a fixture that Craig Brown put them in his Sellar and Yeatman-style garbled history of the 20th century, 1966 and All That, as the ‘Sitford Misters’ – Pecca (the anorexic), Recca (the anarchist), Decca (the record producer). They had become so famous they were ripe for parody.

It is salutary, then, to encounter this big, sympathetic book by a leading American academic, which takes Jessica (Decca) Mitford’s life and work seriously. Set apart from her right-leaning sisters by her devotion to socialism, Decca emigrated to America in 1939, aged twenty-one, and never moved back. A card-carrying communist during McCarthyism, she wrote two classics: Hons and Rebels (1960), a memoir of her childhood, not very popular at home – Nancy at least had the decency to fictionalise everything – and The American Way of Death (1963), a bestselling exposé of the funeral racket. But what makes her an inspirational figure now to Carla Kaplan, a self-described ‘white scholar in Black Studies’, was her commitment to civil rights.

Kaplan’s summary of the family background emphasises pluck. Decca’s mother, Sydney Bowles, aged eight, braved a year-long journey aboard the family yacht, which her father sailed through Syrian storms. During a visit to the Redesdales’ estate of Batsford at the age of fourteen, Sydney had a fishbone stick in her