Why Every Classic Companion Left Doctor Who
8. David Brierley - K9 Mark II
When John Leeson left Doctor Who to pursue more on-camera roles, he was replaced as the voice of K-9 by David Brierley. The change of actor was explained by K-9 - a robot dog - contracting a form of laryngitis! Brierley then voiced K-9 in four stories, including the unfinished serial Shada.
Soon, Brierley began to have the same concerns as John Leeson and requested an on-screen role in season 18. This request was denied by producer John Nathan-Turner, and so Brierley chose not to reprise the role of K-9 for another series.