Lucia di Lammermoor – like La sonnambula – had become associated with light-voiced sopranos, so when Callas took on the title role in the early 1950s she proved revelatory with her combination of visceral power, technical refinement and interpretative insight. In 1955, she and the La Scala company visited Berlin to perform Lucia and the result was what the Germans call a ‘Sternstunde’ – a shining hour. It brought her together with another musical titan, Herbert von Karajan, and the results were phenomenal, the more so for a cast that also included the tenor Giuseppe di Stefano, the baritone Rolando Panerai and the bass Nicola Zaccaria.