While the Doctor has a rest, Romana finds the fourth segment of the Key To Time on Tara, only to be kidnapped by the villainous Count Grendel. It transpires that Romana is an exact double of Tara's Princess Strella. Grendel has aspirations to the Taran throne, and has kidnapped Strella in an attempt to force her to marry him; now he believes he can make Romana pose as Strella and accomplish the deception that way. But the Doctor allies himself with Reynart, Strella's true love, in a desperate attempt to stop the throne from falling into Grendel's cruel grasp.

Producer Graham Williams had designed Doctor Who's sixteenth season to be comprised of six serials detailing the Doctor's search for the missing segments of the Key To Time. Consequently, many of the year's details had to be nailed down at an early stage. By January 1978, five of the six stories had already been decided upon. The first four adventures would be The Ribos Operation by Robert Holmes, The Pirate Planet by Douglas Adams, The Stones Of Blood by David Fisher and “Shield Of Zarak” (also called “The Doppelgangers”) by Ted Lewis. The season would conclude with Bob Baker and Dave Martin's The Armageddon Factor, leaving only the fifth slot undecided.

Script editor Anthony Read had been very pleased with Fisher's work on The Stones Of Blood, and as the writer completed that serial, Read decided to approach him about contributing the season's remaining adventure. At about the same time, “Shield Of Zarak” fell through, as Lewis battled personal demons. This adventure had dealt with the notion that legendary figures like Robin Hood might not be as benevolent as their tales allege. Read asked Fisher to come up with a storyline in the same swashbuckling vein, and suggested a send-up of Anthony Hope's 1894 novel The Prisoner Of Zenda. Fisher agreed, and was commissioned to write “The Androids Of Zenda” on May 26th.

The same day, Robert Holmes was contracted to write The Power Of Kroll, which was intended to replace “Shield Of Zarak” as the season's fourth story (designated Serial 5D). A Doctor Who veteran (and Read's predecessor as script editor), it was felt that Holmes would be able to put together a workable adventure in short order. By now, Michael Hayes had been assigned to direct Serial 5D. Originally an actor, Hayes subsequently began to take off-stage duties in theatre, radio and television. He co-produced the early BBC science-fiction serial A For Andromeda and later directed episodes of programmes such as Z Cars and Play For Today. He had previously worked with Read on The Troubleshooters and with Williams on Softly, Softly: Task Force. Unfortunately, as Holmes' scripts for The Power Of Kroll began arriving in mid-June, Hayes became very concerned about the feasibility of its technical demands.

By this point, Fisher had also started submitting his scripts for Serial 5E. This was now called The Androids Of Tara; in the interim, other titles considered had apparently included “The Androids Of Zend”, “The Prisoners Of Zend” (or “The Prisoner Of Zend”) and “The Seeds Of Time”. (The latter was part of a short-lived effort to unify the titles of all the Key To Time stories under the format “The [Something] Of Time”.) After speaking with Hayes, Williams agreed to interchange The Androids Of Tara and The Power Of Kroll in both the production and broadcast schedules. This meant that Fisher's adventure was now identified as Serial 5D, and chronicled the search for the fourth segment of the Key To Time.

In constructing his scripts, Fisher broadly followed Hope's outline for The Prisoner Of Zenda, and included many analogous characters. Prince Rudolf became Prince Reynart (so called after Renart the fox, the French folkloric character popularised in Pierre de Saint Cloud's twelfth-century novel Le roman de Renart), Antoinette de Maubin became Madame Lamia (named for a female demon in Greek mythology), Sapt became Zadek, Fritz von Tarlenheim became Farrah, and Princess Flavia became Princess Strella. The novel's two chief villains, Duke Michael and Rupert of Hentzau, were combined into the person of Count Grendel (whose name was drawn from the antagonist of the epic poem Beowulf). The role of the novel's hero, Rudolf Rassendyll, was essentially shared by the Doctor and the android “George”. The Archimandrite's title, meanwhile, was actually that a senior abbot in orthodox Christian churches.

Fisher set his scripts on the planet Tara, after the ancestral seat of the kings of Ireland (and, according to mythology, of the supernatural Tuatha dé Danann). He had hoped that Tara might be populated by animals resembling creatures of legend, such as unicorns (which might be natural or mechnical), and originally envisaged Till as a dwarf rather than a hunchback. Fisher was very proud of Count Grendel, and decided to have him escape death at the climax of The Androids Of Tara so that he might potentially be brought back for a return appearance (although, in the event, no such story was ever formally planned).

Although Fisher had constructed his scripts so that Castle Gracht could be realised in the studio, Hayes was able to secure permission to film in and around Leeds Castle in Leeds, Kent. This would serve as both Castle Gracht and the Taran countryside. The first day at Leeds was July 24th. One of the scenes recorded on this day was of the Doctor fishing. During one take, Tom Baker inadvertently tossed the antique fishing rod he was using into the water; stunt arranger Terry Walsh had to dive in and rescue it. Later that day, Hayes engaged his son, Patrick, to make the bushes rustle to signify the approach of the Taran Beast. Filming continued at Leeds Castle through to the 28th. On this day, another water-related mishap occurred when the sound recordist fell into the moat while shooting the scenes of K-9 in the boat.

Studio recording on The Androids Of Tara was divided into a pair of two-day sessions. The first of these took place in BBC Television Centre Studio 6 on August 14th and 15th. Scenes recorded on the 14th included those in the TARDIS, the android surgery, Strella's room in the palace and Strella's cell. The next day dealt with some of the material in and around the dungeon, particularly Prince Reynart's cell.

The second studio block encompassed August 28th and 29th, and was now situated in TC1. The first day completed the dungeon sequences, as well as those in the surgery corridor and the coronation room. Finally, the 29th was dedicated to scenes in the great hall, the hunting lodge, the tunnel and the Pavilion of the Summer Winds. Unusually, the opening credits for The Androids Of Tara were recorded such that the episode number appeared prior to the author's name, rather than the other way round.

• 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 #293, 26th July 2000, “Archive: The Androids Of Tara” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who Magazine Special Edition #9, 22nd December 2004, “I'll Put You Together Again” by Andrew Pixley, Panini Publishing Ltd.
• In-Vision #35, December 1991, “Production” edited by Justin Richards and Peter Anghelides, Cybermark Services.