Stengel learnt medicine and psychiatry from Freud, Wagner-Jauregg, von Economo, Schilder and others in Vienna. He was Jewish and fled from Austria to England in 1938. He became professor of psychiatry in Sheffield, one of the first UK chairs of psychiatry outside London. He was renowned for work on suicide and attempted suicide, and for his wit, energy, and sense of humour.

Ismond Rosen was a psychiatrist and sculptor who exhibited at the Royal Academy. Rosen created his original portrait sculpture of Stengel in the 1950s. This head was prepared from the original mould but Rosen abstracted Stengel's hair to symbolise 'his pearls of wisdom, knowledge, and his devilish humour, the latter represented by a horn on the right side.' The sculpture was unveiled in 1991, the 150th anniversary of the founding of the College's predecessor body, the Association of Medical Officers of Hospitals and Asylums for the Insane.