John Rex left his native South Africa after being branded an "undesirable" as a result of his opposition to apartheid, and went on to produce influential work on race relations throughout his career.
Professor Rex was born in Port Elizabeth and served with the Royal Navy during the Second World War. While fighting alongside black soldiers, he became aware of the injustice of the prejudices that would be formalised under the apartheid system.
After returning to South Africa, he started to train as a minister, but changed his mind and completed a degree in sociology and philosophy instead. He began teaching at a mission school in Rhodesia (now Zimbabwe), but then moved to the UK. After completing a doctorate at the University of Leeds, Professor Rex went on to work at the institution between 1949 and 1962 before moving to the University of Birmingham, where he stayed until 1964. He then joined Durham University, where he worked from 1964 to 1970, during which time he founded its department of sociology.
In 1970, he joined the University of Warwick, where he taught until 1979, returning to the institution for a second stint from 1984 to 1990. He set up Warwick's department of sociology and, after retiring from the role of research professor in ethnic relations, accepted an emeritus professorship at the university.
Professor Rex also taught at Aston University between 1979 and 1984, and took on visiting roles at institutions across the globe, including the University of Toronto, the University of Cape Town and New York University.
His academic specialism lay in conflict analysis, and he was well known as an expert on race. He was a member of the United Nations Educational, Scientific and Cultural Organisation's international experts committee on racism and race prejudice in 1967 and served as president of the International Sociological Association's research committee on racial and ethnic minorities between 1974 and 1982.
Although he was vocal about the need for objectivity in academic research, Professor Rex was an outspoken left-wing activist in his personal life and was involved with the Campaign for Nuclear Disarmament and the New Left Review.
Peter Ratcliffe, professor of sociology and director of the Centre for Rights, Equality and Diversity at Warwick, was a colleague and collaborator. He said: "John was the reason that I, and a number of my colleagues, came to Warwick. He was a towering figure in British, indeed international, sociology. I relished [working] with him."
Professor Rex died on 20 December. He is survived by his wife, Margaret, and four children.