Tegan Jovanka (Janet Fielding)
Australian Tegan Jovanka was on her way to start a new job as an air hostess when she entered the TARDIS, thinking it was a genuine Police Box. Shortly afterwards, her aunt was murdered by the Master.
After witnessing the Doctor regenerate into his fifth incarnation, she joined Nyssa and Adric in their travels with the Doctor. Tegan's adventures with the Doctor were especially traumatic: she was present when Adric died, and was mentally assaulted by the Mara on Deva Loka.
Finally sickened by all the death she'd witnessed, Tegan left the Doctor and Turlough, after helping to thwart an attempt by the Daleks to invade time itself.