Helen Mirren on how difficult it was to play someone who was seen as annoying without alienating her as a character, and to do that by showing humanity and reality, on how the film isn't an historic drama about the Tolstoys but a story about love and marriage, on why there aren't more stories about old love and how most films have a happily ever after, on Anne Marie Duff being pregnant and how happy she is for both her and James McAvoy