[2] In 1903 he was appointed professor of New Testament Greek and Exegesis at Mansfield College, Oxford.
In 1911 he moved back to the University of Aberdeen, succeeding William Ramsay as Regius Professor of Humanity, in which position he remained until his retirement in 1937.
The outbreak of World War II prevented its completion within his lifetime, but Souter did publish a smaller work borne of this endeavour, Glossary of Later Latin, A.D.
Souter's two main interests were in the text of the New Testament and in early Latin commentaries on the Pauline epistles.
[2] A public lecture is held annually in the University of Aberdeen in memory of this scholar.