Conception and writing

The Keys of Marinus was written to replace a different script, Dr Who and the Hidden Planet by Malcolm Hulke, which was deemed problematic and required rewrites. The production team approached Terry Nation, writer of the second serial The Daleks, to write the serial. Nation had been due to write Doctor Who's eighth serial, The Red Fort, but had focused on other projects in the interim.^[4] Due to the quick turnaround required for the script, Nation and script editor David Whitaker decided to base the serial around a series of "mini-adventures", each with a different setting and cast; Nation was intrigued by the idea of the TARDIS crew searching for parts of a puzzle.^[5] As the first two episodes were written with mostly interior sets, Nation wanted to tell a story more "out in the open", setting the third episode in a jungle to allow the designer an opportunity for different settings. Whitaker suggested a cold snow-scape setting for the fourth episode to contrast with the hot jungle.^[6] Nation used many existing words for location and character names in the story: Marinus originated from the Latin word marinus, meaning "of the sea"; Morphoton is based on Morpheus, the Greek god of dreams; Millennius came from the term millennium, for a thousand years; and Arbitan is based on the Latin word Arbiter, meaning a judge.^[7] Producer Verity Lambert selected John Gorrie as the serial's director; even though Gorrie was unhappy with the quality of the scripts, he agreed to direct the serial to advance his career.^[8]

Characters and casting

Carole Ann Ford was displeased with the portrayal of Susan in the serial, as she felt that she was written like a child,^[9] describing her character as "pathetic".^[10] By mid-March 1964, the serial's guest cast had been finalised. Veteran actor George Coulouris was cast in the role of Arbitan; Gorrie immediately thought of Coulouris for the role while reading the script, and was delighted when he accepted the part, describing Coulouris as his "hero".^[11] Francis de Wolff was selected to play Vasor, while Donald Pickering played Eyesen. Gorrie cast Henley Thomas as Tarron; the two were old friends who had previously worked together. Robin Phillips, who was also friends with Gorrie, was cast as Altos; Gorrie felt that Phillips' handsome looks fit the role of Altos accurately. Similarly, he wanted the character of Sabetha to resemble a princess, and selected former drama student Katharine Schofield. Gorrie was impressed by the sinister voice of Heron Carvic, casting him as the Voice of Morpho, and the role of Kala was given to Fiona Walker, who had written to Gorrie for a role. For the role of the Voord, among other villains, three young actors, who were friends of Gorrie, were cast: Martin Cort, Peter Stenson, and Gordon Webster.^[12]

Music and design

Norman Kay, who had scored the show's first serial, composed the incidental music for The Keys of Marinus. The score, performed by seven musicians, was recorded in Maida Vale Studio on 7 March 1964; several standard instruments were used, including a clarinet, bass clarinet, double bass, guitar, flute, harp, piccolo, trumpet and percussion.^[13] Nineteen new sound effects were recorded for the serial by Brian Hodgson of the BBC Radiophonic Workshop, including the sounds of the Conscience of Marinus and the clocks in Millennius.^[12] Raymond Cusick, Daphne Dare and Jill Summers were commissioned as the designers for the serial.^[13] Dare based the design of the Voord on a rubber wetsuit, while the heads were created using vulcanised rubber by prop builders Jack and John Lovell.^[14] The submersible props and the Conscience machine were designed by Shawcraft Models.^[15] Cusick used leftover fibreglass to complete the design of the Conscience machine, as the budget was running low.^[16] The moving vegetation in the third episode was constructed by Design and Display Ltd. Jablite polystyrene was used to simulate snow in the third and fourth episodes.^[17] The tank-top worn by Susan in the serial was knitted by Ford's mother.^[10]

Filming

Model filming for The Keys of Marinus commenced in March 1964 at Ealing Studios. For the shots of the wolves in the fourth episode, the BBC purchased 14 feet of film from the 1957 Russian thriller Seryy razboynik (The Grey Robber) from distributor Sovexport. Rehearsals for the first episode took place from 16–19 March,^[18] and weekly recording for the serial began on 20 March in Lime Grove Studios.^[19] Gorrie found the recording days difficult, due to the complexity of the show and the small size of the studio. William Hartnell was absent from the recording of the third and fourth episodes, as he was on holiday.^[9] Ford recalled that the cast could "have a few more giggles" during rehearsals, as Hartnell's tendency to forget lines was time-consuming.^[20] The final episode was recorded on 24 April 1964.^[18] The first episode was edited on 23 March. While most episodes were edited within three hours in an evening, the second episode required two evenings, on 31 March and 2 April 1964.^[21]

Broadcast and ratings

The first episode was broadcast on BBC TV on 11 April 1964, and was watched by 9.9 million viewers, maintaining the audience from previous weeks. The following episode dropped to 9.4 million viewers, while the third returned to 9.9 million.^[22] The third episode became the first Doctor Who episode to be transmitted on BBC1, following its renaming from BBC TV due to the launch of BBC2.^[1] The fourth episode was the serial's most watched, with 10.4 million viewers, followed by a significant drop for the fifth and sixth episodes, with 7.9 million and 6.9 million viewers, respectively;^[22] from the fifth episode, the show's broadcast time returned to its original slot of 5:15pm. The drop in viewers for the sixth episode was attributed to the absence of Juke Box Jury—the programme that followed Doctor Who—which was replaced by the film Where Coco Lives.^[1] The Appreciation Index was an average of 61 for the six episodes, ranging from 60 to 63.^[22]

Critical response

The serial received mixed reviews. Bob Leeson of the Daily Worker felt that the fifth episode of the serial was the show's low point, noting that the introduction of a trial scene represented a rushed script.^[1] In The Discontinuity Guide (1995), Paul Cornell, Martin Day, and Keith Topping felt that the episodic narrative left little room for each story to develop, and that the show's limited budget was evident.^[23] In The Television Companion (1998), David J. Howe and Stephen James Walker praised Cusick's work with a limited budget, and enjoyed the serial's conclusion.^[24] In A Critical History of Doctor Who (1999), John Kenneth Muir lauded the serial's depiction of co-existing—but not strictly interconnected—cultures and the development of their world.^[25] In a 2008 review, Patrick Mulkern of Radio Times wrote that "standards slip appreciably" after the four preceding serials in terms of "ambitious but slapdash" script quality, as well as the below-par sets and supporting characters.^[26]

In 2009, Graham Kibble-White in Doctor Who Magazine derided Susan's character for "devolving into a bit of a shrill", but was generally positive towards the episodic story structure and the timing of Hartnell's holiday. Despite this, he wrote that the final two episodes "never truly engages with the tenets of courtroom drama".^[27] Elliot Thorpe of Den of Geek felt that the episodic story structure "works incredibly well" by keeping the momentum and making each episode "fresh".^[28] In 2010, DVD Talk's J. Doyle Wallis attributed the serial's weakness to the Doctor's absence, the lack of a main antagonist that would thread the episodes together, the "lacking and disparate" world of Marinus, and the "ramshackle" execution of the concept.^[29] Arnold T. Blumberg of IGN described the serial as "a clichéd premise ... handled poorly and with no spark at all apart from Hartnell's late-hour rally". He cited the poor production quality and the "hodge-podge" leaps to various locations on Marinus which were "boring if not inept".^[2]