It may sound like a fluffy children’s yarn, but The Boy In The Striped Pyjamas, based on the best-selling novel by John Boyne, was challenging material for all involved. Rupert Friend and David Thewlis reflect on the experience of playing Nazi officers who try to shield an eight-year-old German boy, Bruno (Asa Butterfield), from the reality of life at a nearby concentration camp. Vera Farmiga, who plays Bruno’s neurotic mother, explains why even the grownups could not grasp the full extent of the appalling crimes against humanity.