Spin-off biographies are dangerously tempting. Researching a major subject always reveals rabbit holes down which the biographer could happily disappear, never to rejoin the main burrow. Often it’s a mistake to go back to the warren at all. But if the author is as accomplished as Peter Conradi, acclaimed biographer of Iris Murdoch, then it’s a journey worth taking.

Frank Thompson was a brilliant, modest, handsome and gentle young man, physically clumsy and engagingly self-deprecating, born in 1920 to Anglo-American parents of strong religious and political beliefs. His father, a poet and Methodist minister, was deeply involved with Indian independence; his American mother grew up in Syria and Lebanon