 In 1962, Armstrong made his film debut with a small role in director Edward Dmytryk’s drama "Walk on the Wild Side", in which he was billed as "Todd Anderson".His first starring role was the title character in "Jason and the Argonauts" (1963), a mortal who betrays the god of Zeus in search of the golden fleece, but his voice was dubbed by British actor Tim Turner, since a majority of the cast were British.Armstrong had only one additional leading role, in the 1965 World War II film "King Rat".