They were called “Bright Young Things” by the British tabloid press. Over in America, “Flaming Youth” was a similar type—daring socially and sexually, but not aristocratic or all that artistic. England’s BYTs exuded privilege, brought to them by class or talent or both, and they glittered between the wars. Cecil Beaton, who was one of them (through wit and vision), documented the glamour, here on view. —L.J.