"Appalling things can happen to children. And even a happy childhood is filled with sadnesses. Is there any other period in your life when you hate your best friend on Monday and love them again on Tuesday? But at eight, 10, 12, you don't realise you're going to die. There is always the possibility of escape. There is always somewhere else and far away, a fact I had never really appreciated until I read Gitta Sereny's profoundly unsettling Cries Unheard about child-killer Mary Bell.