Maria Callas's 1953 recording of Tosca, opposite Giuseppe di Stefano's Cavaradossi and Tito Gobbi's Scarpia, remains one of the greatest of all opera recordings (go here for an insight into the tempestuous recording sessions).

And here is Callas at Covent Garden in 1964, in Franco Zeffirelli's production. The video has been published by Warner Classics, who will be releasing a new box-set of Callas's complete live recordings (newly remastered) later this year, including a recording from this 1964 production of Tosca.