The 480th episode of Doctor Who airs on BBC1. This is the first part of a season-long story arc – the first in Doctor Who’s history – involving the search for the Key to Time. This episode introduces Mary Tamm as Romana, a fellow Time Lord, as well as introducing the White Guardian to the Doctor Who mythos. Iain Cuthbertson (Children Of The Stones) and Prentis Hancock (Space: 1999) guest star. 
.
The Doctor’s TARDIS is diverted to an unknown place. Upon landing, the Doctor meets the White Guardian, a being more powerful than even the Time Lords, who has chosen the Doctor to retrieve the six missing segments of the Key To Time, which will supposedly restore time and space to a more balanced state. With a new version of K9 up and running, the Doctor is keen to undertake this adventure alone, but again, the Guardian chooses a new companion for the Doctor, a Time Lady named Romanadvortrelundar.
The search for the first of the Key To Time’s six segments leads the Doctor, K9 and Romana to an unlikely place for such an item: the backwards planet Ribos. The natives are wrapped up in superstition and tradition, and they’re largely unaware that their planet is being targeted for takeover by the mad exiled warlord Graff Vynda-K. But even the Graff is being targeted on Ribos by a pair of con men who hope he’ll pay handsomely for directions which will supposedly lead him to a lost mine containing enough of the mineral jethrik to fund his operation. And when everyone’s plans are exposed, they believe the Doctor and Romana are the responsible party.
written by Robert Holmes
directed by George Spenton-Foster
music by Dudley SimpsonCast: Tom Baker (The Doctor), Mary Tamm (Romana), John Leeson (voice of K-9), Iain Cuthbertson (Garron), Nigel Plaskitt (Unstoffe), Paul Seed (Graff Vynda-K), Robert Keegan (Sholakh), Prentis Hancock (Captain), Timothy Bateson (Binro), Ann Tirard (Seeker), Cyril Luckham (White Guardian)
Broadcast from September 2 through 23, 1978
LogBook entry & review by Earl Green
Review: A classic Robert Holmes script full of double acts and wry humor, The Ribos Operation was originally just another story before producer Graham Williams – tired of the Doctor’s aimless wanderings and irresponsibility – decided to create a season-long story arc to give the Time Lord more purpose. Ribos was rewritten accordingly, the most striking change being the addition of the White Guardian’s introductory scene and the resulting removal of several scenes later in the story to compensate for the new material. In some places it shows, but not too much.
Also arriving in this story is Romana, in the form of the glamorous Mary Tamm. It’s quite a gear shift to go from Leela to the first incarnation of Romana; she’s not the subservient screamer that so many of her female sidekick predecessors became, but the air of arrogance – toned down later in the season – was both a bit off-putting, and perfectly in character. And fortunately, K-9 is used sparingly here, serving as deus dog ex machina only once or twice in the entire four-part adventure.
The Ribos Operation is not a story you can semi-watch while it’s on in the background. A load of background information and things vital to the plot are imparted in the course of an extremely wordy (and witty) script, and you’ve got to pay attention. This is helped considerably by one of the best lineups of guest actors a Doctor Who story has ever sported, including yet another appearance from Space: 1999’s Prentis Hancock as a stubborn captain-of-the-guard. Almost all of the key guest players are paired off into double-acts with other characters, so there’s a lot of lively banter in between the sparing bits of action.