Arabella Wagstaff

 was a scavenger who helped the Fourth Doctor escape. She took him back to her ship to meet Jelicho Wigg. When they heard a Silex transmission, she went with the Doctor to warn Maxwell Wilberforce Bell about them. She managed to pilot Wigg's ship to drag the pursuing Silex ship away so that the Doctor could try and reprogramme it. (AUDIO: Subterranea)