The Austrian tenor is making his Royal Opera debut as Siegfried in the third instalment of of the Ring Cycle. He explains why operetta prepared him for the opera’s epic demands, and why Wagner’s loutish adolescent is more hero than zero Andreas Schager bursts through the door, crosses the room in a single stride and engulfs my hand in a firm clasp. “Sorry I’m sweaty,” he grins. “I’ve been forging Nothung!” It’s a midweek lunchtime in a cluttered back office at London’s Royal Opera House, but ...