[3] Humphrey joined the staff of the National Institute for Medical Research in 1949, working in the Division of Biological Standards.

In 1975, Humphrey left NIMR to be Professor of Immunology at the Royal Postgraduate Medical School, Hammersmith.

[4][5] In November 1956 Humphrey founded the British Society for Immunology alongside Robin Coombs, Bob White, and Avrion Mitchison.

[1] He delivered the 1981 Croonian Lecture to the Royal College of Physicians on The Value of Immunological Concepts in Medicine.

[7] His paternal aunt was Edith Humphrey, the first British woman to earn a PhD in chemistry and to identify a chiral.