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From TARDIS Index File, the free Doctor Who reference.

"This must be one of the moons of Delta Magna!"
―The Doctor
The Power of Kroll
Series: Doctor Who -
TV Stories
Season Number: Season 16
Story Number: 102
Doctor: Fourth Doctor
Companions: Romana I, K9 Mk2 (does not appear)
Enemy: Thawn
Setting: Delta III
Writer: Robert Holmes
Director: Norman Stewart
Broadcast: 23rd December 1978 - 13th January 1979
Format: 4 25-minute episodes
Previous Story: The Androids of Tara
Following Story: The Armageddon Factor

The Power of Kroll was the fifth story of Season 16 of Doctor Who, and is part of the Key to Time story arc.



The Doctor and Romana arrive on the marsh moon of Delta Magna in search of the next segment of the Key to Time, but are caught in the conflict between the native Swampies and the crew of a chemical refinery. The presence of a gun runner complicates matters, and to make things worse, the Swampies intend to awaken Kroll, the giant god that lives beneath the swamps.



Part 1

Rohm-Dutt gives the Swampies weapons

In the far future on one of the moons of Delta Magna, Delta III, sits a vast methane and protein collection and manufacturing refinery. The staff of four – the bullying leader Thawn, and his technical support Fenner, Harg, and Dugeen – are in charge of the operation. A green-skinned humanoid native called Mensch, one of the Delta Magnans, serves them. These servile people were once the inhabitants of the main planet but were moved to Delta Three when the Earth Empire identified Delta Magna as commercially valuable; sadly for the green-skinned natives, known as Swampies, this is now also the case on Delta Three. Thawn becomes concerned about the possibility of insurrection when he learns both that the environmentalist group Sons of Earth has taken an interest in Delta Three and that the gun-runner Rohm-Dutt is rumoured to be journeying there. Thawn and Fenner head outside the refinery to see if he has arrived, suspecting a mysterious spacecraft which has touched down nearby is Rohm Dutt’s.

The Doctor and Romana have also arrived on Delta Three, searching for the penultimate segment of the Key to Time. However, the Tracer they are using to locate the segment is giving some very strange readings that makes their quarry difficult to pinpoint. They are ambushed by Swampies and Romana ends up getting taken away with Rohm Dutt and a Swampie patrol, while the Doctor is found by Fenner and Thawn and returned with them to the refinery. There he displays a bewildering familiarity with the methane catalyzing process, with the refined protein then shot into space for delivery to Delta Magna. The Doctor is also intrigued by the position of Mensch, whom the refinery workers do not even regard as a properly sentient being. The Doctor slips away to try and find Romana, but she has meanwhile got herself into a degree of trouble. The Swampies have tied her to a rock and are prepared to sacrifice her to Kroll, a giant squid creature that lives beneath the swamps and which they worship as a god.

Part 2

When it appears from the waters, Kroll is a vast squid – or rather a Swampie dressed as one. The Doctor unmasks the fake monster and rescues Romana.

Back at the refinery, Dugeen has detected a vast living creature some two miles wide inside the swamp. The Doctor and Romana have meanwhile found reference to the real Kroll in a Swampie testament, which says the enormous creature ate a previous Swampie High Priest and has made three appearances with a fourth due soon.

Rohm-Dutt has supplied the Swampies with weapons but when they are used against Thawn, who is searching the swamps for the Doctor, they are found to be defective and explode whenever fired, resulting in the death of one of the Swampies. Seconds later, a huge tentacle erupts from the water and seizes Mensch, dragging him to his death. In the confusion, Rohm-Dutt calls out to Thawn; his cries go unnoticed however, as everyone's eyes are drawn to the vast squid-like creature that emerges from the swamp, towering above the horizon. Kroll is very real, very large and very hungry. Ranquin attempts to mollify it with prayer, and Kroll disappears beneath the surface of the swamp. Despite Ranquin's belief that Kroll has spared his believers, the monster has simply failed to notice the Swampies, and it is soon drawn to the refinery. One of its tentacles enters a pipeline and soon smashes its way inside, dragging crewmember Harg to his death.

Part 3


The gun-runner is taken as a prisoner back to the Swampie camp, where the Doctor and Romana arrive and introduce themselves to the tribe and its leader Ranquin. The elder decrees all three "dry-foots" will die by the seventh ritual of Kroll: a cumbersome and painful affair involving the stretching of the victims on creepers and wood that will eventually snap their backs. In fear, Rohm-Dutt admits Thawn paid him to sell the faulty weapons to the Swampies as a means to discredit the environmentalist Sons of Earth movement. All three are secured and their punishment begins as a violent storm starts on Delta Three. The Doctor rescues himself, Romana, and Rohm-Dutt with "vocal vibrations", which shatter a window above, allowing the rain to pour in on the vines. This relaxes them enough for the trio to escape, pursued by the Ranquin and his tribe.

The three remaining refinery crew members now decide to redirect the upcoming orbit shot against Kroll. They note the creature is now on the move towards the Swampie settlement. When it reaches there its first victim is Rohm-Dutt. The Doctor deduces that the creature hunts by vibration, and uses this knowledge to keep himself and Romana safe from the tentacles. The enormous Kroll now rises to the surface of the swamp.

Part 4

Kroll attacks the refinery

Kroll destroys the Swampie settlement, killing many Swampies before submerging again.

The Doctor and Romana now sneak back into the refinery and are horrified that Thawn calculates the missile strike will destroy the creature and the Swampies. Dugeen is equally appalled, and when he tries to stop the missiles being fired, Thawn kills him. The Doctor, however, is more successful and manages to disconnect the firing mechanism in the rocket silo. Thawn investigates and finds the two culprits, more convinced than ever that they are Sons of Earth spies too. The tables are turned, however, when the Swampies attack the breached refinery and kill Thawn. Ranquin, who has led the assault, believes the deaths of the “dry foots” will help atone to Kroll, but the creature is now above the swamp again and hurling itself against the bulk of the refinery.

While Ranquin fruitlessly prays to Kroll in an effort to stop the attack, the Doctor orders that all the refinery's equipment be activated, in order to try and confuse Kroll. It has the desired effect, and the attack stops. Ranquin refuses to let his faith in Kroll be shaken however, and upon finding one of Kroll's tentacles, begs his god to destroy the "dry foots." Instead, Kroll simply grabs hold of Ranquin and drags him away to his doom. The remaining Swampies realize the creature is beyond appeasement. It is not, however, beyond science. The Doctor has worked out that Kroll has been magnified to giant proportions by a segment of the Key to Time, disguised as a Swampie relic which the squid creature swallowed along with a previous High Priest. He uses the Tracer to eliminate the giant Kroll and retrieve the fifth segment of the Key.

The Doctor finally saves the refinery from destruction by aborting the automatically scheduled orbit shot, which would have resulted in an explosion, and then tells Fenner, the only survivor of the refinery crew, to use his time wisely until a rescue mission arrives from Delta Magna, and to try to understand the Swampie culture. The Doctor and Romana head back to the TARDIS with another segment of the Key in their possession.




  • The Doctor implies he learnt his high pitched singing technique from Dame Nellie Melba.
  • The Swampies were natives of an Earth colony.
  • The Doctor can't hypnotise people with 'narrow eyes'
  • The atmosphere of Delta III is thin, and the gravity tiny, (not that there is much evidence of either).
  • The Sons of Earth are a non violent political movement who believe that all life originated on Earth, and want to return humanity there, though "none of them can have seen Earth".
  • In Episode 2 a Swampie refers to the altar where Romana was to be sacrificed as the Stone of Blood. The Stones of Blood was the title of an earlier serial in the Key to Time cycle.

Story Notes

  • Working titles for this story included: Moon of Death, Horror of the Swamp and The Shield of Time.
  • The final working title was a short lived idea that all stories in Season 16 were going to be entitled The (Something) of Time.
  • Features a guest appearance by Philip Madoc. Madoc had been invited to play Thawn, however, the invitation was withdrawn. He agreed to play the part of Fenner when Alan Browning, who was slated to play Fenner, fell ill before the start of production.
  • John Leeson, best known as the voice of K-9, appears in this episode as Dugeen, in part because the location of the story rendered the use of K-9 unfeasible. This marks Leeson's only on screen appearance in Doctor Who. (Coincidentally, the end of the previous story, The Androids of Tara offered a practical demonstration of why water and K-9 did not mix).
  • The BBC's Head of Serials, Graeme McDonald was so unimpressed by the set designs in this story that he ordered that designer Don Giles was never to work on the series again. By coincidence, episode 3 includes a line of dialogue in which the Doctor criticizes the decor of the Swampies' execution chamber and recommends its architect be fired.
  • The episodes of this serial are noticably shorter than average. While it was normal at the time for individual episodes to fluctuate between 23 and 25 minutes in length, the episodes of this serial clocked in as little as just over 21 minutes. In addition, Episodes 3 and 4 begin with longer-than-usual reprises of the events leading up to the preceding cliffhangers, both clocking in at close to 90 seconds each.


  • Part 1 - 6.5 million viewers
  • Part 2 - 12.4 million viewers
  • Part 3 - 8.9 million viewers
  • Part 4 - 9.9 million viewers


  • As reported by Doctor Who Magazine, this story was a replacement for one entitled The Lords of Misrule by distinguished screen writer Ted Willis. (Ted Willis never worked on Doctor Who. Thriller writer Ted Lewis, best known for the seminal Get Carter, did work on an ultimately unused Key to Time story, title unknown.)

Filming Locations

Discontinuity, Plot Holes, Errors

  • 'Constellation' is once again used to mean 'solar system'. This is almost more of a "continuity". In the Whoniverse (particularly amongst the Time Lords), the term constellation seems to be frequently used to refer to a star system or group of star systems.
  • The Doctor's reed flute playing doesn't match the music.
  • The Swampies, primitive in other ways, have perfected the art of bookbinding, since their history comes complete with an inlaid leather cover. (And why keep it in a hole in the ground?)
  • The wall of the rocket silo is flimsy enough to wobble at the tap of a hammer.
  • The rain pouring through the broken window doesn't make our heroes wet. It falls straight downwards and onto the drying creepers, meaning only their feet get wet.
  • The Doctor whips his galoshes on and off all through the story.
  • Towards the end of episode 3, the Swampies pursue the Doctor, Romana and Rohm-Dutt. Unknown to the Swampies, Rohm-Dutt is killed by Kroll, however in episode 4 the Swampie leader references pursuing only two escapees, even though he by rights should not be aware that Rohm-Dutt is dead.


  • The Doctor, talking to himself before his final encounter with Kroll, says he is 760 years old. This suggests he is either rounding up (as his age was given as 759 in The Ribos Operation) or he's had a birthday since beginning the Key to Time mission. The latter may actually be the case, as a birthday scene was originally planned for The Stones of Blood but dropped.

DVD, Video and Other Releases

DVD Releases

  • Also released with same stories as Doctor Who: The Key to Time, an extras-laden box set limited to 15,000 in its initial UK release on 24th September 2007, later followed by wide release in Region 1 on 3rd March 2009 as The Key to Time - Special Edition.

Contents (2007/2009 version):

  • Commentary by Tom Baker and John Leeson (carried over from the 2002 set).
  • Variations - A BBC local news programme visits the story location during filming. Includes interviews with Tom Baker and Mary Tamm.
  • In Studio - Raw footage taken from one evening's videotaping, focusing mainly on scenes involving Neil McCarthy, Philip Madoc and John Leeson, plus on-set discussions between Tom Baker, Mary Tamm and the director over how to play one scene.
  • There's Something About Mary - Retrospective on Mary Tamm's tenure on the series.
  • Philip Madoc - A Villain for All Seasons - Featurette on Madoc's multiple roles in Doctor Who.
  • Continuities - Off-air continuity links from the story's original BBC1 transmission.
  • Radio Times Billings - Original listings from Radio Times (DVD-ROM PC/Mac)
  • Coming Soon Trailer - Planet of Evil (2007 UK and Australian version)
  • Photo Gallery
  • Production Subtitles



Main article: Doctor Who and the Power of Kroll

See also

to be added

External Links

  • BBC Episode Guide for The Power of Kroll
  • Doctor Who Reference Guide: Detailed Synopsis - The Power of Kroll
  • A Brief History of Time (Travel) entry for The Power of Kroll
  • The Locations Guide to Doctor Who - The Power of Kroll
Season 16
The Ribos Operation  • The Pirate Planet  • The Stones of Blood  • The Androids of Tara  • The Power of Kroll  • The Armageddon Factor
This page uses content from the English Wikipedia. The original article was at The_Power_of_Kroll. The list of authors can be seen in the page history. As with the TARDIS Index File, the text of Wikipedia is available under the Creative Commons Attribution-Share Alike License 3.0 (Unported) (CC-BY-SA).

This article uses material from the "The Power of Kroll" article on the Dr Who wiki at Wikia and is licensed under the Creative Commons Attribution-Share Alike License.


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