Born in Amble, Northumbria, Dennison represented Newcastle United, Nottingham Forest, Fulham and Northampton in an undistinguished playing career. After a spell managing the Cobblers he joined Boro for their first season back in the old second division.
During his reign he was credited for discovering the prolific Brian Clough and bringing goalkeeper Peter Taylor to the club, thus beginning what would become the most celebrated management partnership in English football history.
His tenure began disastrously with a draw followed by eight straight defeats.
But as the Clough, Peacock, Day and Holliday forward line became established things improved and the team finished fifth three times in five seasons as Dennison came close to finding that elusive promotion blend.
But when the 1962-3 season threatened to bring another mid-table finish, Dennison was told his contract had been terminated. A club statement to the press said the parting was by mutual consent, but Dennison later won £3,200 damages for unfair dismissal.
He went on to manage Hereford United and was assistant manager at Coventry City before retiring to Kent in 1978.