Within living memory, Tehran ruled an oil-rich great power brimming with intellectuals inspired by British democracy. So how did it become an impoverished rogue state at war with the West? In this special Bank Holiday edition, Ali Ansari, professor of Iranian history at the University of St Andrews, takes Roland Oliphant through Iran's tumultuous modern era: from the 1906 Constitutional Revolution and the 1953 coup, to the 1979 ousting of the shah and the 2026 US assassination of Ali Khamenei.