A Retrograde was one of the outlaws who abandoned the colony on Frontios to survive in the wastelands. He was at the head of a group who witnessed Cockerill being dragged underground by a Tractator but made no move to help.
However, when the Tractator halted the process after being distracted by the Fifth Doctor and Tegan, the Retrograde declared that a man who resisted the hunger of the earth could do anything. He knocked out a looter who was fighting with Cockerill and armed his group to take over the colony ship, telling Norna that Cockerill was the man who would save Frontios.
They rounded up the orderlies but Norna informed them that Plantagenet was alive and Brazen and Range were rescuing him. She showed Cockerill and the Retrograde the entrance to the tunnels, where they were greeted by Range, who told them about the Tractators. (TV: Frontios)