The Yorkshireman earned his opportunity following a run of success that yielded British, Commonwealth and European titles. His achievements were sufficient to have a sports centre in his native Bradford named after him.
However, five months after the Ali defeat, Dunn lost all three titles to Joe Bugner.
The intervening years have been difficult. After losing most of his ring earnings when a hotel venture collapsed, Dunn returned to scaffolding, a decision which almost cost him his life.
In December 1989, while working on an oil rig, he fell 40 feet, shattering both legs below the knee. The injuries have responded poorly to treatment and he will undergo further surgery in July.
Now a grandfather, he lives in Scarborough with his wife.