[3] Greenfield served as house physician under Alexander Bruce and helped arrange lectures for Byrom Bramwell during his first year of residency at Edinburgh Royal Infirmary.

[3] Greenfield then became assistant pathologist to Matthew Stewart at the General Infirmary at Leeds in 1912, but returned to Queen Square two years later where he became the chair of pathology, a post he held until his retirement in 1949.

[4] During his first few years as pathologist, he also volunteered for a commission from the Royal Army Medical Corps and was deployed in France during World War I, notably serving during the Great Retreat from Mons.

[1] During his time at the National Hospital, Greenfield collaborated with Farquhar Buzzard on several publications, including research on von Economo’s encephalitis in 1919[3] and Pathology of the Nervous System in 1921.

[5] Greenfield played an important role in defining neuropathology as a distinct discipline, including lecturing to the Royal College of physicians on 'the pathology of the neuron' in 1939.