As part of the Wagner bicentenary celebrations at the Proms, Tom Service is at the Royal Albert Hall for a concert performance of Wagner's mighty Tristan and Isolde, the opera that marked a defining moment in the evolution of modern music. Semyon Bychkov conducts the BBC Symphony Orchestra and Violeta Urmana and Robert Dean Smith are the lovers for whom the sweet embrace of death beckons. Tom talks to writer and Wagnerite Philip Hensher, while conductor and cast explain the herculean physical and emotional endurance the opera demands of them.