Duncan was a six-time World Kickboxing Champion before turning to acting.
One of his first roles was as himself in David McKenzieʼs Perfect Sense before re-joining David in other projects including Starred Up and Outlaw King; Davidʼs first major project since winning an Oscar for Hell or High Water.
Duncanʼs most recent outing on the big screen was as Lara Croftʼs boxing trainer, Terry in the 2018 release of Tomb Raider .