The TARDIS lands on far-future Pluto, which the Doctor is astonished to find orbited by miniature suns and inhabited by humans toiling for the Company. After rescuing a worker named Cordo from suicide, the time travellers learn that the Company keeps humanity crushed by oppressive taxation. They decide to seek out the rebels who lurk in the undercity beneath Megropolis One -- not realising that they have aroused the suspicions of the odious Gatherer Hade, who serves the sinister Collector. To make matters worse, the rebels lure the Doctor into a trap... and Leela's attempts to rescue him may have deadly consequences.

During the Seventies, BBC policy generally forbade script editors from writing for their own programmes. Exceptions were made under exigent circumstances and, during Robert Holmes' first three years as Doctor Who's script editor, this had resulted in him providing no fewer than five adventures, two of them under pseudonyms. He had overhauled The Ark In Space, Pyramids Of Mars and The Brain Of Morbius when earlier versions had run into difficulties, and completed The Talons Of Weng-Chiang when a new job forced the original writer to abandon his commission. Only 1976's The Deadly Assassin had been Holmes' creation from start to finish, having been authorised due to its unique, companion-less nature.

After considering leaving Doctor Who at the end of Season Fourteen, Holmes agreed to remain for an additional six months to help new producer Graham Williams settle into his role. As such, in early 1977, he finally found himself with the opportunity to develop a story without undue haste or constrictive requirements. His narrative would transpose the mores of colonial Britain onto a science-fiction setting; a key influence was a newly-published non-fiction book called The Iron Sun: Crossing The Universe Through Black Holes by Adrian Berry, which postulated the idea of man-made suns. By April, Holmes was working on a set of scripts entitled The Sun Makers, although his formal commission came retroactively on May 30th.

Robert Holmes was able to quickly integrate K·9 into the scripts for The Sun Makers

Aware that co-stars Tom Baker and Louise Jameson had a difficult working relationship, Holmes decided to structure The Sun Makers to keep the Doctor and Leela apart as much as possible. He was also involved in discussions about whether K·9, the robot dog who would be introduced in The Invisible Enemy earlier in the year, should be retained as an ongoing member of the TARDIS crew. By early May, Williams had decided to keep K·9 as a regular character, and Holmes was able to quickly integrate him into the scripts. 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 -- then the agency which handled the collection of taxes in the United Kingdom -- over the levies applied to his income as a freelance writer. Holmes was becoming increasingly frustrated as he tried to navigate a series of seemingly arbitrary and byzantine regulations. With The Sun Makers, he saw an opportunity to lampoon Inland Revenue, and the sphere of finances and taxation in general. To this end, he littered his scripts with satire, most obviously by identifying his chief villains as a Collector -- who was a member of an alien race called the Userers -- and a Gatherer. Holmes also labelled an escape route through Megropolis One as “P45” (an Inland Revenue form number), and even referred to the Company's enforcers as the Inner Retinue. Pluto was chosen as the story's setting because the Greek prefix “pluto-” referred to wealth and riches (although it was derived from Plutus, the god of wealth, rather than Pluto, the god of the underworld).

This new approach to The Sun Makers was very much to the liking of its director, Pennant Roberts, who suggested further satirical elements. 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 barbed commentary in the context of a family programme, and was wary that The Sun Makers might be accused of leftist indoctrination. He particularly disliked the reference to the Collector's race as the Userers, which simply adopted an old-fashioned term for a moneylender. A reluctant Holmes briefly changed their name to the Saurians, before a compromise was reached with Usurians.

Meanwhile, Jameson remained unhappy about aspects of her involvement with Doctor Who. Although Baker had recently made efforts to mend his attitude towards her, he continued to be an often moody and domineering presence on set. Furthermore, Jameson was frustrated that the scripts frequently failed to harness what she considered to be Leela's potential. 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, despite Williams' satisfaction with Jameson's work and his hope that she would remain on Doctor Who, he was gradually coming to realise that a new companion might be needed for Season Sixteen.

One of the challenges faced by Pennant Roberts was to find a roof which could serve as the top of the towering Megropolis One

One of the challenges faced by Roberts' team was to find a roof which could serve as the top of the towering 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 recommended the WD & HO Wills Tobacco Factory in Hartcliffe, Bristol: although not particularly tall, it was very wide, which would achieve the appropriate effect. Facing pressure from his superiors to control Doctor Who's budget, Williams was not keen on travelling such a distance for just a handful of scenes, and suggested that they should instead be performed in the studio, via chroma key. However, Roberts discovered that the Wills Tobacco Factory offered other locations which could replace studio sets -- such as a very long tunnel, for scenes in the P45 return route -- and this enabled him to justify the cost of the trip.

Work at the Wills Factory spanned June 13th to 15th. Roberts intended to start with material on the roof, but Bristol was blanketed by mist and so the first day was instead spent on sequences in the lift and in the subways, plus a shot of the Doctor and his friends hiding in a roof vent. The weather did not improve the following day but, with time running out, Roberts divided the filming between scenes in the tunnels and some of those on the rooftop. Sadly, the mist lingered into the 15th; Roberts was forced to complete his rooftop shots on this day, even though the desired effect was partly spoiled. During the work in Bristol, an extra playing one of the Megro Guards fell ill, and so Wills employee Ron Rogers agreed to take his place; however, Rogers' scene was ultimately cut in editing.

On June 16th, 17th and 20th, more material in the subways and on the main staircase was filmed at the Camden Deep Tube Shelter in Camden Town, London. Unfortunately, Roberts' team fell badly behind schedule 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 in Acton, London. Meanwhile, Roberts had cast Henry Woolf as the Collector. Standing five feet tall, Woolf's profile contrasted sharply with Holmes' script, which described the Collector as an expansive figure in the mould of Hollywood character actor Sydney Greenstreet, perhaps best known for his Oscar-nominated performance as the villain of the 1941 mystery classic The Maltese Falcon.

Studio recording for The Sun Makers began with a two-day session, on July 4th and 5th, at BBC Television Centre Studio 3 in White City, London. On the 4th, Roberts completed Episode One, as well as the closing TARDIS scene from Episode Four and some Episode Two material in the subways and corridors. Williams was unhappy to discover that the Consumcard used by the Megropolis citizenry had been crafted to resemble an oversized Barclaycard. Concerned about the obviousness of the satire and potential intimations of product placement, Williams instructed that the prop be altered, and so coloured tape was added to disguise it. July 5th then saw much of Episode Two completed, alongside Episode Three material in the pump room and the Gatherer's office, as well as corridor sequences for the last two installments.

The delays incurred during location filming left barely any time to record the Collector's “liquidation”

The second studio block took place from July 17th to 19th in TC6. The 17th was dedicated to scenes in the exchange hall and the condenser for Episodes Three and Four, while the 18th saw Roberts record material in the computer complex and the therapy section for Episodes Two and Three. Already uneasy with Leela's confinement in a straitjacket, Jameson was aghast when she was left in her restraints while the rest of the team went on break. Remaining to be completed on July 19th were the Episode Four scenes in the computer complex, plus those in main control for the last two installments. Unfortunately, the delays incurred during location filming contributed to an overrun on this final day, which left barely any time to record the Collector's “liquidation”. Visual effects designer AJ “Mitch” Mitchell was so disappointed with the rushed outcome that he was driven to quit the BBC to work as a freelancer.

Although it was the third Season Fifteen serial to go before the cameras, The Sun Makers was positioned fourth in transmission order. This provided some distance from the second adventure, The Invisible Enemy, which was also set on a human outpost. As such, it was broadcast after Image Of The Fendahl, which had followed it into production. With Doctor Who's timeslot having varied slightly in recent weeks, The Sun Makers consistently aired at 6.05pm. Following the broadcast of Episode Four on December 17th, the programme took a two-week break over the Christmas holidays. Superpets aired in its place on Christmas Eve, while a compilation of the first half of the previous season's The Robots Of Death was screened on New Year's Eve.

• 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.
• Doctor Who: The Complete History #27, 2017, “Story 95: The Sun Makers”, edited by John Ainsworth, 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 #27, October 1990, “Production” edited by Justin Richards and Peter Anghelides, Cybermark Services.