- Assistant Legal Adviser, Foreign and Commonwealth Office, London
(1970-1981; 1984-86)
- Assistant Legal Adviser to the Governor of Southern Rhodesia (1979-80).
- Legal Adviser, British Embassy, Bonn (1981-84)
- Legal Counsellor, Foreign and Commonwealth Office (1986-91; 1994-96)
- Counsellor (Legal Adviser), United Kingdom Mission to the United Nations, New York
(1991-94)
- Deputy Legal Adviser, Foreign and Commonwealth Office (1996-99)
- Legal Adviser, Foreign and Commonwealth Office (1999-2006)
Member of the United Kingdom delegation to various international conferences and meetings, including:
- United Nations General Assembly (1972-73, 1991-94, 2000-2005)
- Third United Nations Conference on the Law of the Sea (1975-81)
- Preparatory Commission for the International Seabed Authority (1996)
- Lancaster House Conference on Southern Rhodesia (1979)
- Paris International Conference on Cambodia (1990-91)
- ‘Two-plus-Four’ Negotiations on German Unification (1990)
- United Nations Security Council (1991-94)
- Dayton Proximity Peace Talks on Bosnia and Herzegovina (1995
- Rambouillet/Paris Meetings on Kosovo (1999)
Leader of the United Kingdom delegation to:
- Assembly and Council of the International Seabed Authority (1995-2000 and 2002-05)
Meetings of States Parties to the United Nations Convention on the Law of the Sea (1995-98, 2005)
- Assembly of States Parties to the Rome Statute of the International Criminal Court (2002-03)
- International Conference on the Revision of the SUA Convention and Protocol (International Maritime Organization) (2005)
Various law of the sea and bilateral maritime delimitation negotiations.
Rapporteur of the UN Committee on Applications for the Review of Administrative Tribunal Judgments (1991-94).