Andrew Marr talks to the conductor Semyon Bychkov about Tannhauser, Wagner's tortured artist, out of place in conventional society. While the scientist Mark Miodownik takes a measure of the world, and asks 'Does size matter?' in this year's Royal Institution Christmas Lectures. Author Susan Hill ponders kindness, grief and miracles and the television screenwriter Tony Jordan forsakes EastEnders to take on 'the greatest story ever told', the Nativity. Producer: Katy Hickman.