John Leeson (in-universe)

In an interview conducted on himself by K9 Mark II, he asked himself where "K9 the actor" currently resided. He replied to himself that the actor currently lived in the darkest parts of the Sussex Downs, keeping bees with his friend Sherlock Holmes. (PROSE: K9)

Behind the scenes
While not made explicit within the story, the actor is obviously meant to be John Leeson. John Leeson was explicitly mentioned in the webcast Tom Baker stars in John Lloyd's lost Doctor Who adventure, The Doomsday Contract, though that source is not currently considered valid.

Information from invalid sources
In 2021, John Leeson starred in the full-cast audio adaptation of The Doomsday Contract by Big Finish and John Lloyd, also starring Tom Baker, Lalla Ward, and Julian Wadham. (NOTVALID: Tom Baker stars in John Lloyd's lost Doctor Who adventure, The Doomsday Contract)