"Dr Harper spent a further nine years conducting research at the Department of Agriculture, Oxford, and a sabbatical as Rockefeller Foundation Fellow at the University of California, Davis, he was in 1967 appointed head of the newly formed School of Plant Biology at Bangor University North Wales.He served as president of the British Ecological Society (BES) (1966–1968) and of the European Society for Evolutionary Biology (1993-1995).