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 zeroAndreas 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 hammering out a magical sword is all in a morning’s work for the world’s most in-demand Wagnerian leading man. Currently in rehearsals for Siegfried – the third panel of Covent Garden’s new staging of the Ring Cycle – Schager plans to spend the afternoon slaying a dragon and rescuing his beloved from an enchanted fire (after a spot of lunch, that is). But for now the tenor has a moment to catch his breath.At 54, Schager is an anomaly in the opera world. Most careers – particularly ones singing Wagne...