Thorn (The Bounty of Ceres)

 was a technician who was part of the crew on Ceres.

He looked after the First Doctor after he was exposed to subzero temperatures. After seeing that the oxygen creation algae was dying he initially thought of letting the Doctor die and putting Vicki Pallister and Steven Taylor in cryo storage to conserve oxygen. He started to despise Moreland and planned his death by causing the hull breaches, computer malfunctions and the maintenance robots going haywire. (AUDIO: The Bounty of Ceres)