The TARDIS lands on Pluto in the far future, where the Doctor is astonished to find the planet inhabited by humans and heated by a number of miniature suns. He, Leela and K-9 discover that the human race has been moved off Earth to do the bidding of the Company, a ruthless intergalactic conglomerate. It is up to the Doctor to uncover the secret of the Company's head, the Collector, while Leela is sentenced to death by steaming.

In the Seventies, BBC policy generally forbade script editors from writing for their own programme. An exception to this rule was Doctor Who script editor Robert Holmes, who had been granted special permission to write a limited number of serials for the show per year. By the time planning for Season Fifteen began, Holmes had already authored four Doctor Who adventures during his tenure (most recently The Talons Of Weng-Chiang), and made significant contributions to several other stories. However, his writing had often been carried out under duress, either to replace an abandoned script or concurrent with significant problems on other serials.

As Holmes prepared to leave Doctor Who in early 1977, then, he found himself with the opportunity to finally write a story which could be given his full attention. Inspired by a non-fiction book called The Iron Sun: Crossing The Universe Through Black Holes by Adrian Berry, which postulated the idea of man-made suns, Holmes conceived an adventure which would transpose Britain's former colonial ways onto a science-fiction setting. Holmes was already working on his scripts, bearing the title The Sun Makers, by the time approval was granted on April 30th.

One fortuitous consequence of Holmes being both a writer and script editor for Doctor Who was that he was well aware that the programme's principal cast might be about to grow by one member. The Invisible Enemy, which was the first serial to go into production as part of the series' fifteenth recording block, featured a robot dog named K-9 who proved popular with both Holmes and producer Graham Williams. By early May, Williams had decided to keep K-9 on as a regular character, and Holmes was able to quickly integrate the character into The Sun Makers. John Leeson, who provided the voice of K-9, was contracted for The Sun Makers on May 30th.

Simultaneously, the serial was undergoing even greater changes due to events in Holmes' personal life. At that time, he was embroiled in a protracted disagreement with Inland Revenue over the taxes applied to his income as a freelance writer, and was becoming increasingly frustrated with the department's seemingly arbitrary and byzantine regulations. Holmes saw an opportunity with The Sun Makers to lampoon Inland Revenue, and the sphere of finances and taxation in general. To this end, he littered his scripts with satire -- referring to the villainous rulers of the colony as a Collector (who was a member of an alien race called the Userers) and a Gatherer, labelling a corridor as “P45” (an Inland Revenue form number), and even using his nemeses' initials to inspire the name of the Inner Retinue.

This new approach to The Sun Makers was very much to the liking of its director, Pennant Roberts, who suggested further satirical elements to Holmes. Roberts, who had most recently worked on The Face Of Evil the year before, also encouraged the inclusion of more female characters. He decided to make Marn a woman, and excised a male member of the Others named Rashif, giving his dialogue to Veet. Williams, however, was less keen on presenting such a stinging spoof in the context of a family programme. He particularly disliked the reference to the Collector's race as “Userers”. This was briefly changed to “Saurians” before a compromise was reached with “Usurians”.

The Sun Makers was scheduled to be the third story in production for Season Fifteen, and so was labelled Serial 4W. However, it was then decided to air The Invisible Enemy as the second serial of the season. Because this adventure was also set on a human colony, The Sun Makers was shifted to fourth in the running order to avoid the appearance of repetition. It would now be broadcast after Image Of The Fendahl, the adventure which was due to go before the cameras after The Sun Makers wrapped production.

Meanwhile, Louise Jameson continued to be unhappy with aspects of her time on Doctor Who. Although Tom Baker's attitude towards her had improved recently, he continued to be an often moody and domineering presence on set, and Jameson also felt that writers were frequently ignoring the potential of the Leela character. Although Jameson was contracted for the entirety of Season Fifteen, thought was briefly given to having Leela killed off at the climax of The Sun Makers. This plan was soon discarded, but although Williams was happy with Jameson's work and wanted her to carry on with Doctor Who, he was gradually coming to realise that a new companion might be needed for Season Sixteen.

One of the challenges faced by Roberts' team was to find a roof which could serve as the top of Megropolis One. To be suitable, such a location would have to provide an empty skyline to give the correct impression of height. Unfortunately, despite many attempts, no appropriate building could be found in the vicinity of London. The problem was finally solved by production assistant Leon Arnold, who suggested filming atop the WD & HO Wills Tobacco Factory in Hartcliffe, Bristol. Williams, who was under pressure from his superiors to control Doctor Who's budget, was not keen on travelling that distance for just a handful of scenes, and suggested that they instead be accomplished in the studio via Colour Separation Overlay. However, Roberts discovered that the Wills Tobacco Factory also offered other useful locations (such as a very long corridor), enabling him justify the cost of the trip.

Work at the Wills Factory spanned June 13th to 15th. In addition to the roof and tunnels, scenes were also filmed in the lift and the roof vent. Unfortunately, the sunshine Roberts wanted for the rooftop scenes never materialised, with Bristol instead blanketed by mist throughout the shoot, partly spoiling the desired effect. While at the Wills Factory, an extra playing one of the Megro Guards fell ill, and so Wills employee Ron Rogers agreed to take his place; Rogers' scene was later cut in editing, however.

Additional filming then took place back in London at the Camden Deep Tube Shelter on June 16th, 17th and 20th, involving more material in the subways and on the main staircase. Unfortunately, Roberts' team fell badly behind at this point, and so several sequences had to be shifted to the studio. Model filming also took place on June 20th, at the BBC Visual Effects Workshop.

Studio recording then began with two days in BBC Television Centre Studio 3. July 4th largely dealt with episode one, as well as the closing TARDIS scene from episode four and some material in the subways for episode two. On this day, Williams was displeased to discover that the “consumcard” used by the Megropolis dwellers had been crafted to resemble an oversized BarclayCard. Concerned about the obviousness of the serial's satire and possible accusations of product placement, Williams instructed that the prop be altered, and so coloured tape was added to mask its origins. July 5th then saw most of part two completed, alongside material in the pump room for part three and the corridors for part four.

The second studio session took place from July 17th to 19th in TC6. The first day was dedicated to scenes in the exchange hall and the condenser, as well as those in the computer complex for episodes two and three. Some of the part four computer complex sequences were then taped on the 18th, alongside material in the therapy section. July 19th involved even more material in the computer complex, as well as in main control. Unfortunately, the delays incurred during location filming resulted in an overrun on this final day. Even then, there was barely enough time to record the Collector's “liquidation”. So disappointed was visual effects designer AJ “Mitch” Mitchell with the outcome that the experience ultimately encouraged him to leave the BBC and for freelance work.

• Doctor Who: The Handbook: The Fourth Doctor by David J Howe, Mark Stammers and Stephen James Walker (1992), Virgin Publishing, ISBN 0 426 20369 8.
• Doctor Who: The Seventies by David J Howe, Mark Stammers and Stephen James Walker (1994), Virgin Publishing, ISBN 1 85227 444 1.
• Doctor Who Magazine #306, 25th July 2001, “Archive: The Sun Makers” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who Magazine Special Edition #8, 1st September 2004, “Nobody Does It Better” by Andrew Pixley, Panini Publishing Ltd.
• In-Vision #27, October 1990, “Production” edited by Justin Richards and Peter Anghelides, Cybermark Services.