The Doctor is called upon by the White Guardian, the embodiment of order and light, to find the six hidden segments of the Key To Time -- scattered throughout time and space -- so that the faltering universal balance can be restored. The first destination is the wintry, mediaeval planet of Ribos, where the Doctor soon discovers that a piece of the priceless mineral jethrik is really a segment of the Key in disguise. But the jethrik is part of a scheme being perpetrated by the wily Garron and his confederate, Unstoffe, to swindle a fortune from the megalomaniacal Graff Vynda-K... and the Doctor is soon embroiled in the con.

Although it would become commonplace in later years, the notion of a story arc being threaded through an entire season of Doctor Who was novel in 1976. This was the year that Graham Williams became the show's producer, and he immediately wanted to take an unprecedented approach to its fifteenth season. Williams was leery of the level of coincidence associated with the Doctor stumbling upon a new adventure in every serial, and also felt that the Time Lord's free-agent status placed him in a morally ambiguous position. Williams thought that it would be more effective if the Doctor was acting on behalf of a higher power, who would send him on a series of missions.

To this end, Williams developed an overarching storyline which would run through all six serials of Season Fifteen, in which the Doctor was despatched by a cosmic force known as the White Guardian to salvage the six segments of the Key To Time. This powerful artefact was essential to maintaining the balance between good and evil in the cosmos, but had been stolen by an agent of the White Guardian's opposite number, the Black Guardian. The segments were now disguised and scattered throughout time and space. During his quest, the Doctor would be racing against the clock -- having been provided with a “candle” whose glow would fade as chaos overtook the universe -- and would also be hampered by acolytes of the Black Guardian.

It became obvious that there wasn't time to implement the Key To Time concept for Season 15

Williams submitted a three-page outline of the story arc on November 30th. However, the production team had to start commissioning scripts early in the New Year, and the Key To Time concept necessitated considerable forward planning and coordination. Consequently, it quickly became obvious that there wasn't enough time to implement Williams' vision; instead, the producer decided to postpone the Key To Time storyline to Season Sixteen.

Towards the end of 1977, Williams and script editor Anthony Read fleshed out the Key To Time format and assembled a potential roster of writers for the season. Amongst them was Robert Holmes, Read's predecessor, who had most recently written The Sun Makers for Season Fifteen before handing over to Read. Holmes had been approached to write that season's concluding adventure as well, but had declined the offer in favour of spending some time away from Doctor Who. Instead, he agreed to write the first adventure of Season Sixteen. This delighted Williams and Read, because the veteran writer could be relied upon to deliver scripts which would require minimal work -- an essential start to a season which promised to be more logistically challenging than usual.

Working to the requirement that his adventure feature no film work of any sort, Holmes devised a narrative called “The Galactic Conman”. The scripts were commissioned on December 9th. The story's setting was patterned after mediaeval Russia, with the name of the planet -- Ribos -- being an anagram of the common Russian name “Boris”. The currency of Ribos, the opek, was a reference to both the Russian kopec (one-hundredth of a ruble) and the Organisation of Petroleum-Exporting Countries, better known by its acronym OPEC. Holmes originally wrote the Seeker as a man and Garron as Australian -- hence the reference to his fraudulent sale of the Sydney Opera House -- although the latter detail would be changed to make Garron a Londoner when Iain Cuthbertson was cast in the role.

During its development, Holmes' serial was retitled “Operation” -- slang for a confidence trick -- and finally The Ribos Operation. Holmes left the opening sequence involving the White Guardian to be written by Williams and Read, while the script editor also contributed the notion that the piece of jethrik was actually the first segment of the Key To Time. Initially, the jethrik was important because it was actually a source of incredible energy which could power a fleet of spaceships.

In addition to kickstarting the Key To Time arc, another important function of The Ribos Operation was the introduction of the Doctor's new companion. Williams had tried until the last minute to convince Louise Jameson to stay on Doctor Who for another season as Leela, but his efforts proved unsuccessful. Choosing to err on the side of caution, Williams had developed a replacement character in the form of a junior Time Lord called Romanadvoratrelundar -- whose diminutive form was originally “Romy” and then “Romana”. Williams conceived Romana as intelligent, aloof and naive, but also surprisingly adaptable; over the course of the season, she would be seen to learn from the Doctor and begin to reject the strict code of behaviour imposed by Time Lord society.

Out of about 2000 applicants for the role of Romana, 6 were selected to audition with Tom Baker

The director assigned to The Ribos Operation, George Spenton-Foster, was brought on board early to help Williams cast the new companion. This would be Spenton-Foster's second and final Doctor Who serial, after working on Image Of The Fendahl the previous year. Out of about three thousand applicants for the role of Romana, six actresses were selected to audition with Tom Baker on February 14th, 1978. One finalist was Belinda Mayne, who would later appear as Delta in Delta And The Bannermen.

To provide a sharp contrast with Leela, Williams pictured Romana as a traditional ice queen -- a blonde in the mould of Grace Kelly, the star of films such as Rear Window and High Noon who had become the princess of Monaco. However, the role ultimately went to the dark-haired Mary Tamm, who had been a classmate of Jameson's at the Royal Academy of Dramatic Art. Although Tamm harboured some misgivings about becoming the Doctor's latest companion, her fears were assuaged by the strength of the character outline, and the production team's assurances that Romana would be more than just another screamer. A press photocall to announce the new castmember was held on February 17th. On March 20th, Tamm was contracted for her first two serials.

A major question mark at the end of Season Fifteen had been the status of K·9 as an ongoing element of Doctor Who. Although the robot dog was very popular with younger viewers, the prop was noisy and broke down often, and the remote control mechanism sometimes interfered with the studio cameras. Williams was reassured that K·9 could be improved, however, and so The Ribos Operation introduced his “Mark II” incarnation. To address the various problems, visual effects designer Dave Havard collaborated on the new prop with K·9 operator Nigel Brackley, who had recently moved from the Radio Control Model Centre to Slough Radio Control in Berkshire. John Leeson was contracted to voice K·9 in The Ribos Operation on February 14th.

In late February, Williams took a holiday in advance of the start of Doctor Who's sixteenth production block. Upon his return, on March 7th, Williams met with Graeme MacDonald, the BBC's Head of Serials. Surprisingly, MacDonald asked Williams to tone down the level of jokiness exhibited in Season Fifteen serials like The Invasion Of Time. This was in spite of the fact that Williams' decision to place an emphasis on humour had been a reaction to MacDonald's instructions to chart a course away from the levels of violence and horror exhibited in Doctor Who during the three-year tenure of his predecessor, Philip Hinchcliffe.

A disagreement arose over who was responsible for lighting the torches which decorated many of the Ribos sets

The Ribos Operation was recorded at BBC Television Centre Studio 4 in White City, London, beginning with a three-day session from April 9th to 11th. Spenton-Foster quickly had to contend with a demarcation dispute amongst the crew, arising from a disagreement over who was responsible for lighting the torches which decorated many of the Ribos sets. The first day dealt with scenes in the relic room and the adjacent areas, including the shaft. On the 10th, Spenton-Foster focussed on sequences atop the tower roof, as well as those in and around the Graff Vynda-K's room. Sets in use on the 11th included those for the city wall, the concourse, and the corner door leading to the Hall of the Dead.

In advance of rehearsals, Jameson had warned Tamm of the difficult relationship which had developed between Baker and herself. As a result, the new lead actress made certain to stand her ground when Baker behaved rudely towards her. This earned her co-star's respect, and they would get along well with each other from that point forward. Nonetheless, Baker did take exception to Romana's bright white dress, which he found distracting. Although it was intended that Romana would always be seen in white -- to reflect the notion of her as an “ice queen” -- these plans were hastily dropped.

A serious incident occurred during rehearsals for the second studio block. One lunchtime, several members of the cast went to a hotel for drinks. They were accompanied by George, a Jack Russell terrier owned by Paul Seed, who played the Graff Vynda-K. Baker started trying to get George to perform a trick in which the dog would leap up to snatch a sausage from between his lips. Unfortunately, George inadvertently bit Baker, necessitating a trip to hospital to treat a deep cut on the left side of the actor's upper lip. Baker was forced to wear a large plaster cast, which was plainly visible in some of the publicity photos for The Ribos Operation. More painfully, the wound had to be concealed using make-up during the final studio session. Fortunately, the nature of the remaining scenes meant that Baker's face could often be partially hidden, so that continuity with the previously-taped material was not completely lost.

Creating further chaos with the rest of the recording schedule were the ongoing labour disputes. Spenton-Foster had planned to erect large coloured screens so that chroma key could be used to enlarge the scale of sets such as the White Guardian's limbo, and magnify the size of the Shrivenzale in the Catacombs. However, the floor technicians could not agree on who should operate the screens, and so the effect had to be largely abandoned. Making its debut during this block was the Key To Time prop, several copies of which had been constructed by Dave Havard. The segments of the Key actually fit together, having been inspired by a puzzle given to Havard by Williams. To ensure that the segments were not confused with one another, the producer kept the props locked in his office, retrieving the appropriate segment only on recording days.

The climax of Episode 4 was significantly altered at a late stage

The second studio session took place from April 23rd to 25th. The first two days involved the completion of the remaining Ribos scenes: in the Hall of the Dead, the Catacombs and the caves. The climax of Episode Four was significantly altered at a late stage. Originally, the Graff did not murder the Seeker himself but instead sent her back to the Catacombs, whereupon the Captain set off the explosion to seal the caves and killed the Seeker in the process. Believing himself to be the prophesied survivor, the Graff -- insane and hallucinating about past campaigns -- then took an ammunition pouch from a supposedly dead guard. The Doctor would reveal himself at this stage while an explosion detonated, heralding the Graff's demise. Finally, April 25th was dedicated to the TARDIS material and the prologue in the White Guardian's domain.

During the twenty-four weeks that Doctor Who was off the air, its timeslot was generally occupied by Saturday Night At The Movies or Rolf On Saturday -- OK? during the spring, and then the American superhero show Wonder Woman over the summer. Episode One of The Ribos Operation aired on September 2nd at the unusually early time of 5.45pm. This was to accommodate the broadcast of The European Athletics Championships immediately afterwards, and meant that Doctor Who aired after Grandstand, a Tom And Jerry cartoon short, and a news update.

The following week, Doctor Who returned to 6.20pm. It was now preceded by the new call-in game show Noel Edmonds' Lucky Numbers and followed by Saturday Night At The Movies. On the 16th, Episode Three was pushed back by ten minutes, due to the transmission of Last Night Of The Proms that night. Finally, the broadcast of Episode Four coincided with another change to the BBC's Saturday evening schedule, with Doctor Who now leading into the rebranded Larry Grayson's Generation Game. Later that evening, the veterinary drama All Creatures Great And Small debuted -- launching the career of Peter Davison, the future Fifth Doctor.

• Doctor Who Magazine Summer Special 1995, “Archive: The Ribos Operation” by Andrew Pixley, Marvel Comics UK Ltd.
• Doctor Who Magazine Special Edition #9, 22nd December 2004, “I'll Put You Together Again” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #28, 2017, “Story 98: The Ribos Operation”, 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 #32, July 1991, “Production” edited by Justin Richards and Peter Anghelides, Cybermark Services.