The other day a stranger approached me in the road and asked whether I was Jewish. In 42 years of life, the question had never been posed to me by someone I didn’t already know. My first wild instinct was to offer congratulations in reply, perhaps a prize for observational skill. I don’t look the part. My father was Scottish, gingery and freckled, and my mother is the stuff of Hitler’s nightmares: a blond, blue-eyed Jew. “I thought so,” said the stranger, their hunch confirmed. We went on to have a confused, uneasy exchange. It was late. The stranger was...