John wrote the first English language book devoted exclusively to Population Geography (1965), setting the agenda for a generation with a focus on “how distribution, composition, migrations and growth of populations are related to spatial variations in the nature of places.” It sold over 100,000 copies and was translated into Arabic, Malay, Orissa and Spanish. His later papers developed themes of scale, population growth, sex ratio, migration and the relation between population and environment. John enjoyed travel and visited 83 countries in all. His research covered many countries in the Middle East, North Africa and West Africa and he had many PhD students from those countries. He edited numerous volumes, often involving international collaboration as he chaired the International Geographical Union (IGU) Commission on Population Geography (from 1980 to 1988) and established a Commission on Population and the Environment within the International Union for the Scientific Study of Population (IUSSP), chairing from 1990 to 1995. From 1990 to 1993 John chaired the International Social Science Council (ISSC) Working Group on Population Data and Global Environmental Change. His low-budget Sierra Leone in Maps (1966) established a much-copied format, and he also edited the innovative laser-printed grid-square atlas People in Britain (1976). In Durham, John established the Census Research Unit, with Dewdney, Rhind, Evans and Visvalingam, initially from 1973 to 1976, but with publications continuing to 1986. After a spell as Acting Principal of Trevelyan College, in 1981 he succeeded his teacher and mentor Bill Fisher (see The Geographical Journal, 1985, 151, pp. 148–149) as Head of the Geography Department. Unlike his predecessor, he served a three-year term and was anticipating the reward of a double sabbatical, but instead was persuaded to accept the appointment as Pro-Vice-Chancellor (PVC) and “Sub-warden” of Durham University. The 196 committee meetings he attended or chaired in 1985 led him to propose a restructuring of PVC duties, with greater division of labour, which was accepted. John was also Director of Development, but had the misfortune to occupy these positions of responsibility during the Thatcher years of cuts in university budgets. John was very active in the Geographical Association, the Institute of British Geographers and the Royal Geographical Society. He was a member of the research committee of the RGS from 1974 to 1981, chaired the RGS Jordan Badia research and development programme from 1991 to 1997, represented the RGS on the British National Committee for Geography from 1976 to 1981, and served as Vice President of the RGS to 1995; he was awarded the Victoria Medal of the RGS in 1991. John was also a member of the Social Science Research Council's Human Geography Committee from 1970 to 1977. He also made a number of radio broadcasts, and was Durham President of the Association of University Teachers between 1975 and 1978. After a second term as PVC of the University of Durham, John retired in 1990 at the early age of 60 and applied his energies to important roles in County Durham. He chaired the Durham and North Durham Health Authorities (1990–1996) and served as Deputy Lieutenant of County Durham: in 2003 he was awarded an OBE for services to the community in County Durham, recognising work for the University, the Health Authority, the National Lottery charity and the County Durham Foundation. John was happily married to Dorothy (known affectionately as Dig by friends and family) from 1955 until her death in 2008, and is survived by their three daughters, and grandchildren. Dig's serious illness in her last 10 years was the saddest episode in a devoted husband's life. Throughout his long and active life John Clarke was above all a very pleasant, likeable and helpful person. He had great influence on population geography and the study of the Middle East and North Africa. John made tremendous contributions to the University and County of Durham. His advice was always welcome, and he remained cheerful and good company to the end, when it was hard for him to bear a steady loss of memory. John was very sociable, an academic leader, an approachable colleague and an influential teacher, and he is missed for all of those qualities.