Tom Stoppard is perhaps the world’s leading, funniest and cleverest playwright. Ever since he hit the ground running in the 1960s with Rosencrantz and Guildenstern Are Dead, there has always been a streak of melancholy beneath the sparkling surface of his work. Now with his latest play, Leopoldstadt, he comes full circle and faces up to the pain and loss in his past. In this programme, he tells Alan Yentob his extraordinary story.