In recent years the world has become an unsettling place, from the mass movements of refugees to political upheaval, both in this country and abroad. Disturbingly, history shows that it's at unsettled times like this that dictators can rise - leaders who promise they can solve every problem, if only they're granted supreme power. David Olusoga examines fifty years of BBC documentary archives to try and discover why dictators can have such a powerful appeal. David uncovers the surprising optimi...