From 1946, he was educated at the Royal Belfast Academical Institution, where, encouraged by his teachers H. C. Fay and John Cowser, he began to develop an interest in Latin literature.
[1] In 1954, Courtney was hired as a research lecturer at Christ Church, a constituent college of the University of Oxford.
Two senior colleagues exerted particular influence on him: the Horace scholar Robin Nisbet and Eduard Fraenkel, the former Corpus Christi Professor of Latin.
[2] He published critical editions of Valerius Flaccus, Juvenal, Statius, Petronius, and of poetry surviving only in fragments (The Fragmentary Latin Poets).
[1] Of the latter, the Latinist Michael Reeve wrote that he knew of no other contemporary scholar "who could have tackled with such erudition an independence of judgement" the topic of fragmentary poetry.