"One final warning, though, which is not about ethics but practicalities. Cheap assassination drones already exist on the battlefield, but as automated weapon technology develops, we may find them being used elsewhere. Are we really prepared for small drones with guns that can look into the windows of Downing Street, or Buckingham Palace? The history of military technology shows that it cannot be kept out of private hands, but we have to hope that killer robots are an exception."