Romana I
The White Guardian originally assigns Romana to assist the Doctor during the quest for the Key to Time, a series of linked serials which constitute the whole of Season 16 (1978–79). Romana first appears in The Ribos Operation, and was intended as a contrast to her predecessor, the savage Leela. Romana is initially haughty and somewhat arrogant, looking down on the Doctor (whom she considers to be her academic inferior) and responding to his initial resentment at her presence with icy put-downs. However, she soon gains an appreciation for the Doctor's experience and sense of adventure, and begins to respect him as a teacher.
Over the course of Season 16, Romana begins to take on some of the characteristics of the screaming "damsel in distress", which reinforced Tamm's decision not to remain in the role as she felt the character had been taken as far as she could go. As a result, Romana regenerates at the start of Season 17, emerging with a different physical appearance and a lighter personality.
Although Tamm had left the show on relatively good terms and was willing to film a regeneration sequence for the start of Season 17, she was not invited to do so. She has stated that the often-repeated explanation that she left due to pregnancy is a myth that was started by producer John Nathan-Turner as she was not pregnant when she decided to leave the series. However, her pregnancy has been stated as the reason she was not able to film a regeneration sequence.
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