 There he went to Penyrheol Comprehensive School.Allen made his stage debut in a Gang Show with the 1st Loughor Scout Troop and was a founding member of the West Glamorgan County Youth Theatre and a member of the National Youth Theatre of Wales, before choosing the Mountview Academy of Theatre Arts over completing his A levels.During the early 1990s Allen had minor roles in the BBC’s The Trials of Oz and in Channel 4's "Look at it This Way".