When the Master steals information about a doomsday weapon, the Time Lords send the Doctor and Jo to the planet Uxarieus in the twenty-fifth century. There, they discover an Earth colony struggling with the twin perils of crop failure and death at the hands of what seems to be a monstrous lizard. Meanwhile, agents of the Interplanetary Mining Corporation have arrived on Uxarieus, asserting their right to drill for valuable duralinium. The Doctor must discover what connects these events with the Master -- and with the planet's primitive natives, who harbour a terrible secret.

When Barry Letts became the producer of Doctor Who in late 1969, he was largely happy with the show's new Earthbound format, which had been introduced by his predecessors, Peter Bryant and Derrick Sherwin, at the start of its seventh season. However, Letts worried that the types of stories which could be told would become repetitive. This was a concern shared by writer Malcolm Hulke, who felt that Doctor Who was now limited to narratives about alien invasions and mad scientists -- although the production team had worked hard during Season Seven to disprove this notion. Hulke himself had contributed The Silurians and had considerably rewritten David Whitaker's The Ambassadors Of Death. For Doctor Who's eighth season, Letts decided to experiment with a return to an alien world, and Hulke was asked to develop ideas.

On June 29th, 1970, Hulke was commissioned for a storyline entitled “Colony”, inspired by the days of the American Wild West, and the strife between European-descended settlers and the indigenous peoples. Hulke was asked to incorporate the Master into “Colony” but, by this stage, Letts and script editor Terrance Dicks were aware that their plan to feature the new archvillain in all five Season Eight stories ran the risk of becoming predictable and boring. As such, it was agreed that Hulke would not bring the Master to the forefront until midway through the serial. “Colony” would see only a minimal presence for the United Nations Intelligence Taskforce (UNIT) characters, with Benton and Yates entirely absent and the Brigadier present only in the opening and closing installments.

Malcolm Hulke imagined the IMC robot as humanoid in form, as opposed to the boxy construction which appeared on screen

For unknown reasons, a revised storyline for “Colony” was commissioned on September 1st, followed by the scripts on September 15th. At this stage, two character names were altered: John Ashe's first name became Robert, and Reeves became Winton. The title was expanded to Colony In Space. The adventure was originally set circa the year 3000, but Mary Ashe would now describe the colonists as leaving Earth in 2471. Hulke imagined the IMC robot as humanoid in form, as opposed to the boxy and machinelike construction which appeared on screen.

The director assigned to Colony In Space was Michael Briant, who had previously been an assistant floor manager on The Daleks' Master Plan and a production assistant on both The Power Of The Daleks and Fury From The Deep. Briant made a significant change to the story by casting Susan Jameson in the role of Morgan, whom Hulke had envisaged as male. However, Head of Serials Ronnie Marsh overruled Briant, fearing that a female character who demonstrated Morgan's sadistic tendencies might leave the BBC open to charges of fetishism. At Letts' suggestion, the part was instead given to Tony Caunter, who had initially been cast in a more minor role. Jameson was told of the decision on January 27th, 1971, although she would nonetheless be paid in full.

Model and effects filming for Colony In Space took place on and around February 6th, at both Caravel Film Studios in Slough, Berkshire and the BBC Television Film Studios in Ealing, London. The Ealing work included the footage of the lizard monster -- really a four-foot-long iguana from the London Zoo which became aggressive towards the camera crew. The venue for the location filming was the Old Baal China Clay Quarry in Carclaze, Cornwall. Work there ran from February 10th to 12th, and then resumed after the weekend for two more days, on the 15th and 16th.

The Carclaze shoot was made arduous by cold, driving rain which generated copious amounts of mud. The inclement weather caused the destruction of the garden planted outside the colonists' dome, and even blew away the tent providing privacy for the portaloo -- while Katy Manning was in the midst of using it! The murky terrain also meant that regular vehicles would be unable to facilitate tracking shots. Fortunately, assistant floor manager Graeme Harper -- later a prolific Doctor Who directing beginning with 1985's Revelation Of The Daleks -- had recommended that Briant use military-grade four-wheeled vehicles called Haflingers for the IMC buggies. Now they would pressed into service by the camera crew, as well.

On March 3rd, during rehearsals for the first studio session, Letts lured Pertwee and Manning out to a BBC parking lot, ostensibly to record a trailer. There, the series star was ambushed by Eamonn Andrews, who revealed that Pertwee was the latest subject of his biographical programme, This Is Your Life. Pertwee's episode aired on April 14th.

Meanwhile, Colony In Space followed the usual Doctor Who recording pattern and was taped fortnightly in two-day blocks, on Fridays and Saturdays. For the most part, Briant opted to devote each day to a single episode. The only exception came during the first session, on March 5th and 6th at BBC Television Centre Studio 4 in White City, London. On the Saturday, Briant chose to record the first scene of Episode Three alongside Episode Two, so that the set for the Leesons' dome would not have to be erected again two weeks later. A former child actor, Briant also decided to provide various voiceovers throughout the serial. However, because he was no longer a member of the actors' union, his performance was credited to Pat Gorman, a frequent Doctor Who extra who would genuinely appear as a Primitive, an IMC guard and a colonist. The rest of Colony In Space was taped in TC3, with the middle episodes recorded on March 19th and 20th, and then the concluding installments on April 2nd and 3rd. Episode Six saw Briant's wife, Monique, make a cameo appearance as one of the colonists.

The first story of Season Eight, Terror Of The Autons, had invited some criticism due to its frightening content. With Letts and Dicks intentionally pitching Doctor Who to a slightly older audience than in the past, the BBC decided to overhaul the Saturday evening schedule, beginning with the transmission of Colony In Space Episode One on April 10th. Doctor Who now aired at 6.10pm, almost an hour late than before. It was preceded by Walt Disney's Wonderful World Of Colour -- which occupied its former timeslot -- and a news update, and led into a Tom And Jerry cartoon short and then a series of movies branded as The Saturday Western. The new schedule paid dividends almost immediately, boosting Doctor Who's audience by more than a million viewers each week.

• Doctor Who Magazine #238, 8th May 1996, “Archive: Colony In Space” by Andrew Pixley, Panini UK Ltd.
• Doctor Who Magazine Special Edition #2, 5th September 2002, “Something Old, Something New” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #17, 2015, “Story 58: Colony In Space”, edited by John Ainsworth, Hachette Partworks Ltd.
• Doctor Who: The Handbook: The Third Doctor by David J Howe and Stephen James Walker (1996), Virgin Publishing.
• Doctor Who: The Seventies by David J Howe, Mark Stammers and Stephen James Walker (1994), Virgin Publishing.