Why Every Classic Companion Left Doctor Who
1. Sophie Aldred - Ace
Introduced in 1987, Sophie Aldred was the last Doctor Who companion of the classic era. Aldred's incredible partnership with Seventh Doctor actor Sylvester McCoy ensured that Doctor Who went out on a high when it was "rested" in 1989. Aldred had planned to leave during the following season had Doctor Who been renewed, and script editor Andrew Cartmel had vague plans for how Ace would leave the show.
However, due to the decision to rest Doctor Who in 1989, these plans never came to pass and Ace continued to be a part of Doctor Who via audio dramas, comic strips and novels. Sophie Aldred later returned to Doctor Who in 2022, opposite Jodie Whittaker's Thirteenth Doctor, and revealing scant details about how Ace left the TARDIS.