What will never be known is the why, what could drive an apparently normal person like Myra Hindley to commit such crimes. Brady was somehow easier to understand: he was strange, a man with an obsession with Adolf Hitler and the Marquis de Sade. But for a woman to take part in the murder of children marks her out as being possessed of an evil beyond our comprehension, an evil that will forever be associated with that famous police mugshot - the peroxide blonde hair, the small, tight mouth, the dark, hooded eyes.