The Invisible Enemy: Part Two
First Broadcast October 8th 1977 @ 6.00pm (7.3m viewers)
The debut of K9 marks a turning point in the development of the programme. ‘The Invisible Enemy’ was Graham Williams’ first story as Producer and he was keen to move away from the dark and grim horror-inspired era synonymous with Robert Holmes and Philip Hinchcliffe. The cliffhanger for Part Three of ‘The Deadly Assassin’ for instance had drawn several complaints. As a result Doctor Who was taken back towards a more family friendly and less horrific style. K9 was a key part of that.

Co-writer Dave Martin had sadly lost two dogs and came up with the idea of a robotic canine. Younger viewers were drawn back having been turned away by the terrors of Krynoids, murderous Voc Robots or the deformed Magnus Greel. They could also easily relate to the appeal of a robot dog. What 8 year old wouldn’t want a friendly computer that could help you with your homework? Adult viewers have however debated K9 more vociferously. Some sections of fandom have dismissed the dog as a bit of a know-it-all. Others enjoyed his sense of humour and the way that actor John Leeson managed to provide an appealing personality through voice and it’s unique design. That design by Tony Harding, produced in a matter of weeks, has become almost as recognisable as the iconic Daleks. Love him or loathe him, K9 is synonymous with a new era of Doctor Who, first appearing during this episode.
Memorable Moment (Spoiler Warning)
“That tin thing is my best friend and constant companion.”

K9 is initially introduced as a peculiarly shaped printer. It then quickly becomes apparent that he is a more than just a machine. “Made up” for Professor Marius, K9 is a quirky computer with vast intelligence. But one armed with a laser and a sense of humour. Immediately the Doctor understands the capabilities of K9, asking him for information on cloning for instance. Also on meeting K9 Leela strikes up a friendship with this supposed inanimate object that would lead to the two departing the TARDIS together at the end of the season. This first appearance would only be the beginning of a journey of stories which have continued for many years since.
The popularity of the metal mutt continues to this day. He was of course, the first to get a spinoff show, with Sarah Jane Smith, the single episode ‘K9 and Company’. K9 returned in ‘The Five Doctors’, ‘School Reunion’, ‘Journey’s End’ and numerous appearances in The Sarah Jane Adventures. In 2009 a K9 TV series was produced in Australia totalling 26 episodes. It also featured a dramatic redesign of the famous dog. The next time we see K9 may indeed be at your local cinema during 2017, fittingly K9’s 40th Anniversary.
Cast:
Doctor Who – Tom Baker
Leela – Louise Jameson
Safran – Brian Grellis
Lowe – Michael Sheard
Professor Marius – Frederick Jaeger
Crew:
Director – Derrick Goodwin
Producer – Graham Williams
Writer – Bob Baker
Writer – Dave Martin
Also First Aired On This Day…
- The Tenth Planet: Episode One
- The Sarah Jane Adventures: Eye of the Gorgon: Part One