An Antarctic expedition unearths two pods which the Doctor recognises as Krynoids. Once germinated, the pods will infect humans, turning them into giant carnivorous plants which will quickly overrun the world. Already Winlett, one of the expedition members, has started to succumb to the Krynoid taint. To make matters worse, the insane botanist Harrison Chase has learned of the pods' existence and has despatched the sadistic Scorby to obtain them. Even if the Doctor and Sarah are able to stop the mutating Winlett in Antarctica, an even greater threat awaits them at Chase's mansion in England...

The story originally intended to conclude Doctor Who's thirteenth season was The Hand Of Fear. Writers Bob Baker and Dave Martin submitted their idea to script editor Robert Holmes on May 29th, 1975, and were commissioned to write a six-part serial on June 20th. A week later, Douglas Camfield was contracted to direct the story; he had recently completed the season premiere, Robert Banks Stewart's Terror Of The Zygons. As development continued on The Hand Of Fear, however, producer Philip Hinchcliffe became increasingly concerned that the serial had too many problems to be resolved before it entered production. Holmes was preoccupied with rewrites on the year's penultimate adventure, The Brain Of Morbius, and so it wasn't until late September that he was able to assess Baker and Martin's scripts. He quickly came to share Hinchcliffe's misgivings, and they concluded that The Hand Of Fear would have to be redeveloped for Season Fourteen.

With no alternative six-part story available, Hinchcliffe and Holmes sought permission from Bill Slater, the BBC's Head of Serials, to shorten Season Thirteen by two episodes. This would allow them to replace The Hand Of Fear with a four-part serial already in development; candidates included Eric Pringle's “The Angarath” and a second script from Stewart, who had been in conversation with the production team during the summer. When Slater denied their request, Hinchcliffe and Holmes instead decided to expand Stewart's adventure to six episodes. On September 30th, he was commissioned to write The Seeds Of Doom. Stewart was asked to work very quickly, since Camfield had already begun pre-production, including location scouting. As such, the director was afforded considerable influence in the serial's development.

It was agreed that the first two installments should form an almost self-contained prologue set in the Antarctic

Several elements of The Seeds Of Doom echoed The Quatermass Experiment, Nigel Kneale's seminal 1953 television serial about an astronaut who transformed into a plant creature due to an alien infection. In order to extend the original four-part narrative to six episodes, Stewart and Holmes agreed that the first two installments should form an almost self-contained prologue set in the Antarctic. Here they drew upon another science-fiction classic: the 1951 movie The Thing From Another World, in which a scientific expedition discovered and revived a hostile alien lifeform buried in an Arctic glacier. Stewart christened his monsters Krynoids, also spelt Crinoids or Crynoids; a crinoid was actually a type of echinoderm, a marine animal also known as a sea lily or a feather-star. Harrison Chase's first name was originally Harrington, while Amelia Ducat's surname was inspired by Stewart's childhood music teacher.

For the last time in the Seventies, The Seeds Of Doom featured the involvement of the United Nations Intelligence Taskforce (UNIT). The organisation had been a Doctor Who fixture since 1968's The Invasion, and had played a key role during Jon Pertwee's tenure as the Third Doctor. Since taking the reins of the programme, however, Hinchcliffe and Holmes had been slowly diminishing the prominence of UNIT. This escalated in The Seeds Of Doom through the omission of any of the regular UNIT characters. Instead, the roles normally filled by Brigadier Lethbridge-Stewart and RSM Benton were given to two new characters, Major Beresford and Sergeant Henderson.

To the production team's relief, Stewart was able to deliver his scripts for The Seeds Of Doom within three weeks. During this time, designer Jeremy Bear fell ill after working on the sets for the Antarctic camp; Roger Murray-Leach was quickly brought onto the production to replace him. As a cost-saving manoeuvre, the costume for the humanoid version of the Krynoid was adapted from an Axon outfit, originally created for 1971's The Claws Of Axos. The major alteration was a change in colour scheme from orange to green but, at one point, tufts of hair were meant to be added, to represent the last vestiges of the mutated human.

The main location work for The Seeds Of Doom took place at Athelhampton House in Athelhampton, Dorset, from October 30th to November 3rd. The manor, built in the late fifteenth century by Sir William Martyn, served as the exterior of Chase's estate. The cottage where Keeler was hidden was River Cottage, on the grounds of Athelhampton House; it was situated next to the River Piddle, where Scorby met his end. Unusually, Camfield elected to record the Athelhampton material using Outside Broadcast video rather than film, to facilitate the visual effects for the expanding Krynoid.

Model shots of the Krynoid and Chase's mansion were captured on November 6th at the BBC Television Film Studios in Ealing, London. Further model work, involving the Antarctic base, occurred around the same time at the BBC Television Centre Puppet Theatre in White City, London.

The studio schedule for The Seeds Of Doom followed the usual pattern of fortnightly recording on Mondays and Tuesdays. The first block, encompassing November 17th and 18th, was assigned to BBC Television Centre Studio 4. Most of Episode One was recorded on the Monday, although there were concerns that the final scene was too terrifying. Afterwards, Kenneth Gilbert (who played Dunbar) discovered that he had contracted chicken pox from his daughter, forcing his absence until the last of the three recording sessions. Almost all of Episode Two was taped on the Tuesday, alongside a more subdued version of Episode One's cliffhanger. More misfortune occurred that night, when Michael McStay (Moberley) was involved in a traffic accident after leaving the studio, suffering both a fractured skull and a broken leg.

Taping resumed on December 1st and 2nd, again in TC4. The majority of Episode Three was recorded on the Monday, as was Episode Four material in the special projects lab and the effects shot of the Krynoid cutting the phone line in Episode Five. The Tuesday concentrated on Episode Four, in addition to scenes in the general lab and the cottage bedroom for Episode Five, plus those in Dunbar's office for each of the final two installments.

On December 7th and 8th, Camfield's team headed back out on location. This time, their destination was the grounds of Buckland Sand and Silica Company Ltd in Buckland, Surrey; recording again took place on OB video. The quarry was principally dressed as the Antarctic wastes, although the limousine chauffeur's Episode Three attack on the Doctor and Sarah Jane was also taped there. On the 8th, while Tom Baker and Elisabeth Sladen were performing the closing scene outside the TARDIS, the police box prop collapsed on them. It had been in use since Doctor Who began in 1963 -- enduring several refurbishments over the ensuing fifteen years -- but would now be retired and replaced.

Tom Baker became verbally dismissive of the scripts, unaware that Robert Banks Stewart was in the production gallery

The final studio block took place on December 15th and 16th, this time in TC8. Both Gilbert and McStay were able to rejoin the production, with the latter wearing a false beard to hide the scars he had received in the car crash. The Monday was largely devoted to Episode Five, as well as Dunbar's remaining scenes from the first four installments. A morning session on the Tuesday saw recording occur at the main entrance of Television Centre itself, which posed as the headquarters of the World Ecology Bureau. Returning to TC8 in the evening, Episode Six was completed, as was material in the compost crusher room for Episode Four, and Episode Five scenes in Dunbar's office and the general lab. Camfield was unhappy with the scripted version of Chase's demise, in which he was thrown into the crusher by the Doctor. Assistant floor manager Sue Shearman suggested the alternative action of Chase's accidental fall into the crusher. Meanwhile, Baker became verbally dismissive of Stewart's scripts, unaware that the writer was visiting in the production gallery. When Stewart confronted him about his comments, Baker quickly apologised.

Work on The Seeds Of Doom then wrapped up on December 19th, when special effects shots of the giant Krynoid were captured in TC4. This brought Doctor Who's thirteenth recording block to an end, and marked the culmination of fifteen months of production for Baker and Sladen, dating back to The Sontaran Experiment at the start of the twelfth block. Having now spent three years on the programme, Sladen was finding herself turning down increasingly attractive work, including a film. As such, she informed Hinchcliffe of her intention to leave Doctor Who after making two more serials for Season Fourteen.

The transmission of The Seeds Of Doom was nearly met with disaster, as the master tape of Episode One was misplaced and Hinchcliffe was forced to consider re-editing the remainder of the serial. Fortunately, the missing tape was located prior to its broadcast on January 31st, 1976. On this day, Doctor Who aired fifteen minutes later than usual, at 6.00pm, due to the inclusion of a Tom And Jerry cartoon short after the news. Conversely, Episode Two was broadcast a quarter of an hour early, at 5.30pm. This was due to Grandstand's extended coverage of the Winter Olympic Games from Innsbruck, Austria, which immediately preceded the news and Doctor Who. The Olympics also impacted Episode Three; with Walt Disney's The Mouse Factory restored to the schedule in-between Grandstand and the news update, Doctor Who aired at 5.55pm. The final three episodes of The Seeds Of Doom reverted to the usual 5.45pm timeslot, albeit with Jim'll Fix It replacing It's Cliff -- And Friends in the timeslot following Doctor Who.

Doctor Who's thirteenth season concluded on March 6th, ending a run which had seen the programme cement its status as one of the BBC's crown jewels. As with The Brain Of Morbius, however, The Seeds Of Doom came under fire from Mary Whitehouse of the National Viewers' and Listeners' Association, who criticised its violent content and the inclusion of a Molotov cocktail. Meanwhile, The Seeds Of Doom would prove to be the final Doctor Who serial for both Robert Banks Stewart and Douglas Camfield; soon thereafter, the acclaimed director would develop a story idea called “The Lost Legion” for Season Fourteen, but it would ultimately go unmade.

• Doctor Who Magazine #263, 8th April 1998, “Archive: The Seeds Of Doom” by Andrew Pixley, Panini UK Ltd.
• Doctor Who Magazine Special Edition #8, 1st September 2004, “Bohemian Rhapsody” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #25, 2018, “Story 85: The Seeds Of Doom”, edited by Mark Wright, Hachette Partworks Ltd.
• Doctor Who: The Handbook: The Fourth Doctor by David J Howe, Mark Stammers and Stephen James Walker (1992), Virgin Publishing.
• Doctor Who: The Seventies by David J Howe, Mark Stammers and Stephen James Walker (1994), Virgin Publishing.
• In·Vision #13, February 1989, “Production” edited by Justin Richards and Peter Anghelides, Cybermark Services.