There was never any mystery about the fact that Louis Feutren, a French teacher at St Conleth’s school in south Dublin, was a Nazi collaborator. He had a taste for violent punishments and bizarre humiliations that terrorised pupils. He liked to reminisce about the second world war, when he had joined a Breton nationalist group that fought on the side of Germany. And he showed pictures of himself in uniform. To have a staff member who was a known Nazi collaborator and fugitive from French justice was accepted at St Conleth’s, which employed Feutren from 1957 until his retirement in...