He held the following positions: Lecturer, Department of English, University College, Swansea 1938-46; Lecturer in Mediaeval English, Oxford University 1946-48; Lecturer in English, Christ Church, Oxford 1946-47, Student 1947-48; Forbes Professor of English Language and General Linguistics, Edinburgh University 1948-64, Forbes Professor of English Language 1964-79 (Emeritus), Honorary Consultant, Institute for Historical Dialectology (formerly Gayre Institute for Medieval English and Scottish Dialectology) 1986-2005; President, Scottish Text Society 1977-89, Honorary President 1989-2005; FRSE 1978; Director, Middle English Dialect Atlas Project 1979-86; FBA 1989; Honorary Senior Research Fellow, Department of English Language, Glasgow University 1993-2005.