During the years 1933 to 1938 he was employed at the Bodleian Library as an assistant in the Department of Western Manuscripts. Liddell then lived briefly in Athens, Greece, working as a lecturer for the British Council. During the years 1941 to 1951 he was a lecturer at the Universities of Cairo and Alexandria.
From 1953 to 1972 he was employed by the University of Athens, serving for part of the time as head of the English Department.
He never returned to England, and died in Athens in 1992. While at Oxford he met the novelist Barbara Pym.
The character of Doctor Nicholas Parnell in Pym"s novel Some Tame Gazelle was inspired by Liddell. During World World War II he was one of the Cairo poets.