Complex sentence: He was elected Master of Selwyn College, Cambridge in 1956, retiring in 1983; two years later, he was named Dixie Professor of Ecclesiastical History, during which time he chaired the Archbishops' Commission on Church and State (1967-1971).
Split into simpler sentences: He was elected Master of Selwyn College, Cambridge in 1956, retiring in 1983. Two years later, he was named Dixie Professor of Ecclesiastical History, during which time he chaired the Archbishops' Commission on Church and State (1967-1971).