"In theory it was a massive bank-balance-breaking fine," John Foster told CBC News.
"When I worked out the fine ... I needed a calculator," he said, estimating the actual fine would have been in excess of £8,577, or just over $14,000 CAD.
Foster, who taught English at UBC from 1974 to 2002, was in Vancouver this summer and found the book — The Poems of Arthur Hugh Clough — while clearing out a storage locker.
"What amazes me is that I somehow overlooked the due date in 47 years," he says.
When he returned to Belfast from his summer trip to Vancouver, Foster says he emailed the librarian at Queen's University Belfast, saying he had a book that was "a bit overdue."
"I was delighted they wanted the book back after all these years," says Foster.
Foster still isn't sure how the book came to be in his possession.
He completed his undergraduate degree at the university, but by the book's due date — October 11, 1966 — Foster says he was a doctoral student at the University of Oregon.