[7][8] Starting his career after WWII, from September, 1945, to May, 1946, Duff fought fourteen bouts in the greater London area, winning twelve, with only one loss and one draw.

He eventually achieved a 75% winning boxing record in a career that included around fifty fights, but lost his last professional bout on December 7, 1948, against Scottish boxer Neil McCearn, in West Ham, in an eight round points decision.

As Solomons' ironclad control of British boxing waned, a new team began to form with Duff as match maker, Jarvis Astaire as manager, and friend and mentor Harry Levene, as promoter.

[10] During his strong position as a promoter and manager, he was involved with at least 16 world champions and many leading British fighters, including: The clout and connections that Duff could bring to bear from his media contacts, wealth, and professional associations could fast channel a competitors rise to a championship bout.

[9] Eventually giving in to diminishing health, loss of his boxing stable, and Frank Warren's dominance through his partnership with ITV and Sky TV, Duff retired.