"We knew not whether we were in heaven or on earth." One thousand years ago, this testimony to the splendour of the Greek Church in Constantinople persuaded the ruler of medieval Russia to choose Orthodox Christianity as the state religion. This choice had profound consequences for the development of Russia, helping to isolate it from the West and contributing to a sense of mystery which is still felt today. The history of the Russian state is inextricably linked with the Orthodox Church. The Church has consistently safeguarded national consciousness, despite centuries of invasions, internal conflict and oppression. This week the Russian Orthodox Church celebrates its millennium. How has it been able to survive when the state has taken on different forms, some alien to its doctrines, and what effect has this had on the Church in Russia?