Philip Glass is so prolific a composer that it is tempting to wonder whether he has become entrapped by his trademark restlessly repeating patterns. At the age of 77, there is no diminution of his prodigious energy; The Trial brings his tally of operas to some 30 since he first shot to fame – or notoriety – with Einstein on the Beach in 1976. Glass is, in effect, an iconoclast-turned-icon, and he is now by far the most performed contemporary composer of opera on the planet.