He then worked at the Lister Institute of Preventive Medicine, obtaining a PhD, also from London University.
[1] From 1955 to 1960, he was a member of the scientific staff of the Microbiological Research Establishment, now part of the Defence Science and Technology Laboratory (or 'dstl' for short) based at Porton Down, near Salisbury, Wiltshire, and usually simply referred to as 'Porton Down'.
Crumpton then joined the scientific staff at the National Institute for Medical Research based in Mill Hill, London, becoming Head of the Biochemistry Division from 1976–79 and the Cell Board from 1979–1983.
Crumpton was a member and later chairman of the World Health Organization’s steering committee for Polysaccharide encapsulated bacteria from 1984–1991.
[1] Crumpton gave the Bernal Lecture in 2004 entitled: "Are low-frequency environmental fields a health hazard?".