The Power of Kroll

The Fourth Doctor and Romana have arrived on the third moon of Delta Magna, searching for the penultimate segment of the Key to Time. They find themselves caught in the middle of a dispute between the crew of a methane refinery and the natives (known as 'Swampies'). The Swampies claim that the crew have disturbed the waters, and will incur the wrath of their god, Kroll. Kroll is revealed to be a giant squid, which surfaces to feed every few centuries and is the source of the abnormally large amount of methane being mined. Originally a normal size squid, Kroll ingested the fifth segment of the Key to Time and began to grow, becoming a god-like figure to the Swampies and their descendants.

After Kroll awakens and begins to attack both the Swampies and the refinery indiscriminately, the Doctor uses the tracer to retrieve the segment of the Key, which destroys Kroll and instigates cellular regeneration within the creature to produce hundreds of normal-sized squid. This process not only saves the planet's inhabitants but removes the source of methane from the refinery. The Doctor and Romana return to the TARDIS and set off on their next adventure.

When script editor Anthony Read asked Robert Holmes to write the story, there were two requirements: that it include the largest monster in series history and that Holmes minimise the humour that many scripts from the era were known for. This second requirement was a request from higher up at the BBC. Early titles for the story were Moon of Death and Horror of the Swamp. Holmes said that he considered the idea of a large monster a mistake given the budgetary constraints at the BBC and named The Power of Kroll as his least favourite Doctor Who story.

Extensive location filming took place in Snape, Suffolk around the River Alde from Monday 18 September 1978 to represent the marshes featured in the script. Nine days of location filming were afforded to the serial, including two night shoots, more than is usual for a Doctor Who story. Studio sequences were taped during October 1978.[1] The serial was directed by Norman Stewart, who had directed the Underworld story a year previously. This was his final assignment on the programme. The actors playing Swampies were coloured green with a special water-resistant dye ordered from Germany. Unfortunately, the make-up artist failed to order the special dye remover, with the result that many of the actors had to take chemical baths to get the green dye off, and many had a green tint for a long period after production was finished. Costume designer Colin Lavers introduced a new tweed coat for the Doctor, which sported four flying duck brooches on its lapels. Around this time, producer Graham Williams fell ill and his duties were taken on by Anthony Read and production unit manager John Nathan-Turner, assisted by Blake's 7 producer David Maloney.[2]

Part One was broadcast only a few hours after BBC1 had come back on-air following a strike. The channel had ceased transmitting programmes after the early evening news on Wednesday 20 December and the dispute was resolved in time for services to resume at 3pm on Saturday 23 December. (BBC2 had been similarly affected, and BBC Radio operated a reduced service.)[5] This disruption accounts for the large drop in ratings compared with the preceding episode, Part Four of The Androids of Tara, which was watched by 9m viewers. By contrast Part Two of The Power of Kroll aired during the week between Christmas and New Year, when viewing figures are often higher, and was watched by nearly twice as many people as Part One: BBC ratings were also boosted by a strike which had taken the Yorkshire region of ITV off-air for the entire Christmas period.[5]

In their book The Discontinuity Guide (1995), Paul Cornell, Martin Day, and Keith Topping wrote that The Power of Kroll was "very slow" with little humour, and "horribly acted" aside from Madoc and Abineri. They also criticised the "unconvincing" realisation of Kroll.[6] In 2011, Mark Braxton of Radio Times gave a negative review of the serial, describing it as uninteresting with poor effects, "tepid dialogue and dull characters". However, he felt that some parts were "enlivened by Tom Baker's sprightly performance".[7] DVD Talk's Justin Felix gave the story two and a half out of five stars, calling it the "least inspired" story of The Key to Time. While he praised Baker and Tamm and their dialogue, he criticised the "flimsy" concept and the Swampies.[8]

The Power of Kroll was voted at #174 by readers of Doctor Who Magazine in a 2009 poll of the top 200 stories — the fifth lowest of any Tom Baker story.[9]

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• The Power of Kroll at BBC Online