My interests lie in the law of the Roman empire in the third to seventh century, and in that of the western successorstates in that period. Further, in the usus modernus, particularly the Roman-Dutch law.
- Emeritus Fellow, All Souls College (from 2014)
- Regius Professor of Civil Law, University of Oxford and Fellow of All Souls College (from 2006 to 2014)
- Professor of History of Ancient Law, History of European Private Law and German Private Law, Johann Wolfgang Goethe University Frankfurt am Main (from 1997 to 2006)
- Reader and Acting Chair for Legal Techniques, University of Amsterdam (from 1989 to 1997)
- Lecturer for Legal History, later Senior Lecturer for Legal Techniques, Utrecht University (from 1978 to 1989)
- Undergraduate Postgraduate, University of Leiden and Postgraduate Research Assistant, University of Amsterdam (to 1978)
- Roman and civil Law
- Papyrology
- History of European private law
- History of European colonial law
- Editorial member of the Tijdschrift voor rechtsgeschiedenis
- Editor of the Studia Amstelodamensia
- Corresponding Member of the Royal Netherlands Academy of Arts and Sciences (KNAW)
- Member of the KNAW Committee for the Edition of the History of The Dutch Legal Science
- Vice-President of the Accademia Romanistica Costantiniana
- Member of the General Board of the ‘Stichting OVR’