A Dalek trooper was a mercenary under Gustave Lytton. He, along with Lytton's other mercenaries, helped the Daleks rescue Davros from a prison station.
While on 20th century Earth, he was exterminated by a Dalek loyal to Davros. (TV: Resurrection of the Daleks)
Behind the Scenes
Jim Broadbent was considered for the role.