World War II. English children take a machine gun from a downed Luftwaffe plane and use it as the centrepiece of a lair they build in the grounds of a bombed-out home. Just what kids would do. But human nature messes up their cosy game. Other kids want the gun. The police and the Home Guard are looking for it. And when adults start panicking at the (imagined) threat of a German invasion, events take a possibly lethal turn. It all ends well, but not happily. Once again, a children’s book that belies that category title. There are a lot of uncomfortable insights tucked away inside this gripping little story – which may well explain why it’s sold more than a million copies. It stays in your mind long after you finish it.