'Bellini’s Norma is an epic and multi-faceted role, often considered the ultimate vocal challenge for an operatic soprano. Callas sang it on stage 92 times, more often than any other heroine, and her achievement casts a long shadow: more than 50 years after her last performance in the role (Paris, 1965) she remains the point of reference for any soprano who aspires to it. It was in 1952, as Norma, that she made her debut at London’s Royal Opera House, the theatre that witnessed her final operatic appearance 13 years later. In the famous duets that Norma shares with her fellow druid priestess, Adalgisa, Callas is partnered by another superlative singer, Ebe Stignani, the greatest Italian mezzo-soprano of her era. Taking the small role of Norma’s servant Clotilde is a singer who in 1952 was destined for great things, and for the role of Norma…' Joan Sutherland.