Watkin's his most memorable big screen role came in 1992 with his portrayal of the mad-eyed bodgie, Uncle Les, in Peter Jackson's splatter zombie comedy Braindead. He also became a fixture on the New Zealand small screen, first appearing in early 70s serial drama Pukemanu as the small town doctor, later developing a speciality as villains in productions aimed at kids, like Nutcase and The Mad Dog Gang.
Watkin appeared as Jim in the television movie of Roger Hall's play Glide Time before it was adapted as the early 80s sitcom Gliding On, in which Watkin didn't appear. Though he played Jim again in the post Rogernomics 1998 Gliding On sequel Market Forces.
In 1995, Watkin appeared in Shortland Street as Ted Coombes, a truckie who drunkenly drove his rig into the clinic in that year's Christmas episode.
After supporting roles in the NZ-made Hercules: The Legendary Journeys and his final NZ film, Savage Honeymoon, Watkin went to live in Australia and became a wine merchant.
Watkin grew up in Greymouth before shifting to Wellington to begin acting while working as a magazine editor for the New Zealand Broadcasting Corporation.