As he acknowledges in the foreword to "Iron Kingdom", living in West Berlin in what turned out to have been the last years of the divided Germany (1985-87) gave him an insight into German history and society. He received his Ph.D at the University of Cambridge. He is Professor in Modern European History at the University of Cambridge and a Fellow of St. Catharine's College.

Clark is a co-editor of the scholarly book series New Studies in European History from Cambridge University Press. He is the author of a study of Christian-Jewish relations in Prussia (The Politics of Conversion. Missionary Protestantism and the Jews in Prussia, 1728-1941; Oxford: Oxford University Press, 1995); a critical biography of the last German Kaiser (Kaiser Wilhelm II; Harlow: Longman, 2000, series "Profiles in Power"), and a best-selling history of Prussia (Iron Kingdom. The Rise and Downfall of Prussia, 1600-1947; London: Penguin, 2006). He is also the co-editor with Wolfram Kaiser of a transnational study of secular-clerical conflict in nineteenth-century Europe (Culture Wars. Catholic-Secular Conflict in Nineteenth-Century Europe, Cambridge: Cambridge University Press, 2003), and the author of numerous articles and essays.

Clark is a Fellow of the Australian Academy of the Humanities.

He is married to the art historian Dr Nina Lübbren, to whom he dedicated "Iron Kingdom" and who warmly acknowledged his support and assistance in her own academic work. . They have two sons, Josef and Alexander.

Books

• Iron Kingdom: The Rise and Downfall of Prussia, 1600-1947. Allen Lane, Penguin, 2006. Published in the USA by Harvard University Press. Published in Germany as Preussen: Aufstieg und Niedergang 1600-1947 by DVA, 2007
• Kaiser Wilhelm II. Longman, 2000 (in the series "Profiles in Power")
• The Politics of Conversion: Missionary Protestantism and the Jews in Prussia, 1728-1947. Clarendon Press, Oxford University Press, 1995

Books edited

• Culture Wars: Secular—Catholic conflict in Nineteenth-Century Europe. (with Wolfram Kaiser) Cambridge University Press, 2003