David Ralph Martin was an accomplished television and film writer. He contributed numerous scripts for the Doctor Who television series between 1971 and 1979 in collaboration with Bob Baker. Baker and Martin's most notable contributions to the Doctor Who mythos were probably the robot computer K-9 (created for The Invisible Enemy) and the renegade Time Lord Omega (created for The Three Doctors, Doctor Who's tenth anniversary story).Together they were nicknamed "The Bristol Boys" by the Doctor Who production teams with whom they worked. They also worked together on the 1975 children's science fantasy television serial Sky and Into the Labyrinth.
In the early 1980s, Martin wrote a series of 4 small illustrated children's stories starring K9. In 1986, he wrote the Doctor Who Make Your Own Adventure book Search for the Doctor.
Heh, K-9 is a little smug in this one as he doesn't have emotions so can't be scared by the titular beasts (spoiler for a kids' book from 37 years ago)
Here we have K9 sent to investigate an outbreak of catatonic insanity among the crew of spaceships working in the Vega system; he is assisted (all too briefly) by a Professor Romius (obviously not Romana). In the end K9 saves the day by taking over the mind of the (unnamed) spaceship captain using his extendable data probe, something we've never seen him do before or since, to appreciate what the humanoid crew are experiencing (which that they are under attack by the Beasts of Vega). These turn out to be imaginary monsters playing on emotion; K9 having no emotion is smugly immune, which rather oddly twists the Cybermen's weakness into being an advantage. As it turns out, however, this is setting up that audacious concept, a character arc for K9, to be developed in the next two books.