Why Every Classic Companion Left Doctor Who

Much like a dog playing fetch, John Leeson has left and returned to Doctor Who on a number of occasions. He was first cast as the voice of K-9 in The Invisible Enemy, and remained with Tom Baker through the remainder of season 15 and the entirety of 16. As K-9 became an overnight sensation, Leeson was concerned that his lack of on-screen exposure in Doctor Who would hamper future work.

And so Leeson was replaced by David Brierley for the whole of season 17, and enjoyed roles in shows like Blake's 7 in the interim. When David Brierley left the role of K-9, Leeson agreed to return for the tin dog's send-off. While John Nathan-Turner decided that K-9 should be written out, he did have eyes on a potential spin-off opportunity - the ill-fated K-9 & Company.