The first-night audience for Peter Grimes at La Scala, Milan, was not unprepared for Benjamin Britten's opera. Fragments had been performed at the Venice International Festival last September, to be followed by two complete radio performances from Rome under Fernando Previtali. Yet on March nth, as the curtain rose—the rebuilt auditorium victoriously obliterating memories of bomb-havoc in a symphony of white and gold—one sensed an atmosphere of keen curiosity concerning this rare phenomenon, an English opera.