Sir Derek Bowett, who has died aged 82, earned a formidable reputation as the Whewell Professor of International Law at Cambridge University, as a lawyer with an extensive practice before international tribunals, and as a member of the United Nations International Law Commission. He was an outstanding teacher and a robust, straightforward lawyer, quick to cut to the heart of problems and find practical solutions.
Born in Manchester, Bowett attended the Cathedral choir school and William Hulme's school. He volunteered for the Royal Navy in 1944 and joined the Fleet Air Arm, though the war was over before he was deployed. He served for three years in the navy and, in 1948, went to read law at Downing College, Cambridge, of which he later became an honorary fellow. Though Bowett thought many of his teachers lazy and dull, he had a high regard for Professor Sir Hersch Lauterpacht, then Whewell Professor of International Law. After graduating, Bowett moved to a lectureship at Manchester University, at the suggestion of Lauterpacht and married Betty Northall there. He also studied for the bar, and wrote his doctoral thesis on the law of self-defence, which was published as a book, Self-Defence in International Law, in 1958; it is still quoted today. He took leave from Manchester in 1957-59 to work for the UN in New York and spent a further two years as a UN lawyer, as general counsel to the UN Relief and Works in Beirut from 1966.
Bowett left Manchester University to take up a fellowship at Queens' College, Cambridge, in 1960 and, in 1976, he was appointed reader in international law at Cambridge. By then his book, the Law of International Institutions, first published in 1963, had reached its third edition and he had also published United Nations Forces: a Legal Study of United Nations Practice (1964), The Law of the Sea (1967), and a monograph, The Search for Peace (1972), as well as a host of papers.
Queens' College was quick to recognise his abilities, and, aged 43, he was elected its president, a measure of the trust the fellowship had in him and his wife. They lived in the Lodge, one of the oldest college buildings, on the banks of the Cam, in which Bowett sometimes fished early in the morning. He stayed in the post from 1970 to 1982, during which he brought the construction of Cripps Court to a successful conclusion, completing the largest building project in the college's 550-year history.
Bowett was elected to the Whewell chair at Cambridge in 1981. He is remembered as a first-rate teacher: kind, concerned, clear and comprehensive. He was a scholar firmly embedded in the positivist tradition, who saw with a clarity sometimes lacking in contemporary legal scholarship the difference between a rule of law and a worthy aspiration. In 1982, with a vision of life's possibilities unusually broad for an academic, he stepped down as president of Queens', though he remained a professorial fellow, committed to his work as a teacher, until he retired from the Whewell chair in 1991.
Alongside his teaching, Bowett continued at the bar, where he took silk in 1978 and where his longhand drafting of complex documents are still recalled with awe. Pleading before international tribunals, notably the international court of justice and the Iran-US claims tribunal, he combined clarity with the presentation of sharp, thoughtful arguments testing the limits of orthodox legal principles. While representing foreign governments in various cases, he also found time to serve from 1973 to 1977 on one of the more productive British public bodies, the Royal Commission on Environmental Pollution.
After his retirement from the Whewell chair, he continued in legal practice and sat for five years as a member of the UN International Law Commission. He was appointed CBE in 1983, and knighted in 1998.
In 2007 he recorded a series of interviews for the Cambridge law faculty recalling his career, which are published on its website. The transcript, with its unaffected identification not only of those he respected as inspirations, but also those he regarded as lazy, poor lawyers or fools, preserves an authentic echo of the Bowett voice, immediately recognisable by those who knew him.
He is survived by Betty, a daughter, and two sons.
• Derek William Bowett, lawyer and academic, born 20 April 1927; died 23 May 2009