David Hemblen was an English actor who frequently worked in Canadian film, television and theatre. He grew up in Toronto, Ontario, where he pursued a classical education before turning to theatre. He received an M.A. in English and was working towards a Ph.D. in medieval studies when he was spotted during a rehearsal of a university production by Clifford Williams of the Royal Shakespeare Company. Hemblen was offered a season at Toronto's Royal Alexandra Theatre. Hemblen's career in theatre included many productions at the Stratford Festival and four seasons at the renowned Shaw Festival in Niagara-on-the-Lake. He received a Dora Award nomination for Best Actor for his portrayal of Dr. Astrov in Toronto's Tarragon Theatre production of Uncle Vanya. He also received a Genie Award nomination as Best Actor in Family Viewing.

Hemblen's television career began in the early 1970s, and he appeared in a number of Canadian television series, including The Beachcombers, Night Heat, and Street Legal. He also had recurring roles in the American series T. and T. and The X-Files.