During his lifetime he held the following positions: Assistant in History, Glasgow University 1924-25, Lecturer 1925-34, Senior Lecturer 1934-45; Professor of Modern History, Queen's University, Belfast 1945-53; Burnett-Fletcher Professor of History, Aberdeen University 1953-62; Vice- President, Selden Society 1954-86; FBA 1962; Kenan Professor of History, New York University 1967-68;