Written by Ian Marter, based on Bob Baker and Dave Martin’s scripts for the 1975 TV serial.

Having distinguished himself with an acclaimed novelisation of The Ark in Space, Marter turns his attention to another Season 12 story – and the shortest TV serial to be adapted to date. The result typifies all the author’s obsessions: icky body horror, oily secretions, quivering flesh meeting serrated metal and a streak of voyeuristic sadism.

While this broadly follows Baker and Martin’s scripts, Marter hones in on the Experiment aspect of the title, going into much grislier detail of Styr’s Mengele-like research than would have been contemplated for TV. Human bodies are stripped, bound, stretched, choked, whipped, burnt and crushed as Styr watches with undisguised glee. And he’s just as into psychological torments, subjecting Sarah Jane to a series of mentally scarring experiences. It’s torture porn two decades before the phrase was coined: Hostel for tots.

Styr himself is half cyborg, half middle-aged pervert: a fat, blubbery creature with “wobbling folds” and foul breath introduced declaring, “Aaaaaaaaaaaa… The female of the species…”, who watches a semi-naked spreadeagled man being tortured with “his features swelling and throbbing with pleasure.”

Centring Styr’s kinky experiments (which are repeatedly said to be interfering with his actual mission of scouting out the galaxy in readiness for a Sontaran invasion) allows Marter both to expand the scope of the novel beyond anything shown on TV, and provides a genuinely horrible opponent. The Doxtor, in contrast, is mercurial and compassionate. Sarah Jane boldly stands up for herself, and Harry gets to play a more central and heroic role than on TV as he explores underground tunnels and ultimately penetrates Styr’s (much larger) spaceship to sabotage it and destroy the monster and his dormant crew.

No one else gets much of a look in – which is true to the scripts. The GalSec colonists are largely victims to be picked off, and the Scavenger robot, one of the least successful elements of the production, is dialled right down in Marter’s telling. The result is an outright horror novel which, in its stunning Roy Knipe dust jacket, had a huge impact on me as a kid, and remains a discomfiting, disturbing read. Grade 1.

Next Time: Doctor Who And… The Hand of Fear.