Kirk started wrestling as "Mucky" Mal Kirk after his rugby league career. After a period of time spend wrestling in Germany, where he tagged with Baron von Raschke, Kirk returned to the United Kingdom, now heavier and bald, wrestled as Kojak Kirk then Killer Kirk before changing his ring name to "King Kong" Kirk. Kirk always wrestled as a "heel" (bad guy) and often tagged with the superheavyweight Giant Haystacks in tag-team matches against blue-eyes (good guys). Kirk's work rose to its prominence in the 1970s and 1980s due to the popularity of televised wrestling in the United Kingdom and he was recognised as a consistent heel. Unlike a number of wrestlers at the time, he didn't rely on a wrestling gimmick during his time in professional wrestling. Kirk instead used his physical size and bald head in a manner of appearance which was viewed as legitimately intimidating. However he was viewed by his peers as being a good worker. Canadian wrestler Bret Hart said about his first match with Kirk: "Kirk turned out to be a great worker and bump-taker, and when he collapsed on top of me, he was as light as if he'd covered me with a blanket." Despite being a heel, outside of the ring he was good with children and made himself approachable.