On Start the Week Mary Ann Sieghart explores how far leaders and governments have shaped our world. Matt Ridley dismisses the assumption that history has been made by those on high, whether in government, business or religion, and argues for a system of evolution in which ideas and events develop from the bottom up. The historian Tom Holland revels in the antics of the house of Caesar, from Augustus to Nero, and how this imperial family greatly influenced the ancient world. Barry Cunliffe tells the story of the beginnings of civilisation across Europe and the Far East over the course of ten millennia while the curator Julia Farley concentrates on one of those groups - the Celts - and celebrates their distinctive stylised art in a new exhibition at the British Museum.