Paul Silverthorne has led the viola section of the London Symphony Orchestra for 25 years, working with the finest conductors and musicians in the world. So what does he really think of them, and what has he learnt about the art of conducting? Viola player Paul Silverthorne retires from the London Symphony Orchestra this year, after nearly 25 years – he played his last concert with the group on Monday, 5 October, and returns for a performance at St Luke’s on 13 November. I in