He had large reserves of stamina due to an abnormally slow heart rate, known as bradycardia, and he would use his left jab to score points whilst using his mobility to keep away from his opponent's punches.
This did not always lead to an attractive contest earning him the nickname the one armed bandit, and Cullen was not as popular outside his native North-East as his talent would seem to merit.
He grew up in Wheatley Hill, County Durham, beginning work as an apprentice pipe fitter at the local colliery.
The fight took place on 20 May 1963 at Belle Vue, Manchester, and Charnley retained his title after fifteen rounds with a points decision.
In October of the same year Carlos Ortiz, the Puerto Rican world lightweight champion, came to England for a ten-round non-title fight against Cullen at the Empire Pool, Wembley.
In the meantime, Dave Charnley, had moved up to welterweight and finally retired in December 1964, leaving the British lightweight title vacant.
This incensed some of the home crowd, who made their feeling clear, but Cullen easily gained the decision and became the new British lightweight champion.
Cullen fought two more bouts, gaining points victories before defending his title against Vic Andreeti, the Hoxton fighter whom he had beaten twice already.
Cullen again won on points over fifteen rounds in front of a packed hall, despite a late scare due to a cut near his eye.