- Vice-Master, Downing College and Head of Department (from 2007)
- Professor of Historical Geography and Demography (from 2003)
- University of Cambridge, Director, Cambridge Group for the History of Population Studies and Fellow, Downing College (from 1994)
- Reader in Historical Demography, Cambridge (from 1994 to 2003)
- Quondam Fellow, All Souls College (from 1994)
- Reader, History of Medicine and Director, Wellcome Unit for the History of Medicine, Oxford (from 1990 to 1994)
- Senior Research Fellow, All Souls College (from 1983 to 1994)
- University Lecturer in Historical Demography, University of Oxford (from 1983 to 1989)
- Tutor, Fitzwilliam College, Cambridge (from 1979 to 1983)
- Assistant Lecturer in Historical Geography, University of Cambridge (from 1974 to 1983)
- Postgraduate, St Catharine’s College, Cambridge (from 1967 to 1974)
- Undergraduate, University College London (from 1964 to 1967)
- Medieval English peasant inheritance practices and their impact on property exchanges and social and kinship networks
- Problems of the use of manorial court rolls for the analysis of medieval marriage practices
- Historical demography
- The social history of medicine
- President, Economic History Society
- Co-editor, Economic History Review
- Co-editor of Cambridge Studies in Population, Economy and Society in Past Time
- Editorial board of Continuity and Change
- Editorial board of The History of the Family
- Geographical Tripos (Undergraduate Level—Historical Geography and Historical Demography)
- MPhil in Geographical Research
- MPhil in Economic and Social History
- PhD supervision in Historical Demography, Agrarian History and Historical Geography
- AHRC (2006–9) Private law and medieval village society: personal actions in manorial courts 1250–1350 £380,000.
- ESRC (2008–11 jointly with Dr M. Davies, University of London) Life in the Suburbs: Health, Domesticity and Status in Early Modern London £886,363.