Why Every Classic Companion Left Doctor Who
6. Sarah Sutton - Nyssa
Sarah Sutton's guest appearance in The Keeper of Traken so impressed producer John Nathan-Turner that he gave Nyssa a full-time slot in the TARDIS in the following story. Nyssa quickly became Peter Davison's favourite companion, saying that she best suited his approach to the Fifth Doctor.
Davison was disappointed to learn that - midway through Sutton's second series as Nyssa - she was in discussions to leave Doctor Who. Sarah Sutton and John Nathan-Turner agreed that Nyssa would depart in Terminus, a story that the actress was hugely disappointed by.
Perhaps in protest, Davison and Sutton broke JN-T's rule about on-screen affection between Doctor and companion by sharing a chaste kiss goodbye at the end of the story.