BBV's next series was a spin-off from two "Doctor Who" stories in the 1970s in which the Doctor assisted the United Nations Intelligence Taskforce (UNIT) in defeating the Autons, robotic invaders sent to conquer Earth on behalf of the alien Nestenes. The trilogy, beginning with "Auton" in 1997, recounted UNIT's battle against another Auton invasion, this time without the Doctor's aid (since BBV had obtained permission to use UNIT and the Autons, but permission to use the Doctor himself was as always unavailable). "Auton" was also the first BBV production to have no "Doctor Who" guest stars at all, after Nicholas Courtney (who would have reprised his "Doctor Who" role as UNIT commander Brigadier Lethbridge-Stewart) was forced by ill health to withdraw from the project. With Courtney out, the focus of the series was the original character of Lockwood, an enigmatic UNIT agent played by Michael Wade.