A few years ago, a senior Japanese central banker let me in on a secret side of his life: Like some others in his rarefied world, he is a passionate devotee of Sherlock Holmes. After formal meetings in capitals around the world, he joins other Sherlock Holmes buffs over drinks or dinner for trivia competitions, to test their knowledge of obscure plot details, or to share amateur historical research into Victorian London.

It is all very casual, but the camaraderie is important to him. Through this informal fan club, the banker told me, he had made his closest professional friendships. "I feel closer to many of these people than to many of my countrymen," he said.