Michael Berkeley talks to physicist Sir John Enderby, emeritus professor of physics at the University of Bristol and an expert on neutrons and the medical applications of evanescent waves. Music has been a passion with him since the age of 15, and his choices include the Prelude to Act III of Wagner's Lohengrin, the Easter Hymn from Mascagni's opera Cavalleria Rusticana, a Mahler song, a movement of a Mozart horn concerto and Yonty Solomon playing the first movement of Beethoven's Waldstein Piano Sonata.