‘Can the ultimate betrayal ever be forgiven?’ screams the publicity for The Judas Passion, transforming a Biblical drama into a spears-and-sandals soap opera in a sentence. Thankfully, this really isn’t the premise of composer Sally Beamish and poet David Harsent’s new oratorio. Instead, the two authors pose a more interesting problem: is betrayal still betrayal when it’s divinely ordained, the price of salvation? A performance of Mahler’s Fourth Symphony this week celebrated the innocent joys of heaven; The Judas Passion invited us to count their sinful cost.