The Key to Time

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The Key to Time
The Key to Time DVD cvr.jpg
Cover of the 2008 Region 2 DVD release
Country of originUnited Kingdom
No. of episodes26
Original networkBBC One
Original release2 September 1978 (1978-09-02) –
24 February 1979 (1979-02-24)
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The Key to Time is the umbrella title of the sixteenth season of Doctor Who. The arc was originally conceived by producer Graham Williams, who had proposed it as part of his application for the producer's job in 1976.[1] The name refers to the powerful artefact, the segments of which are what the Fourth Doctor and his companions, Romana and K9 search during the season.


A figure calling himself the White Guardian commissions the Doctor and K9, assisted by a new companion, the Time Lady Romana, to find the six segments of the Key to Time, a cosmic artifact resembling a perfect cube that maintains the equilibrium of the universe. Since it is too powerful for any single being to possess, it has been split into six different segments and scattered across space and time, disguised by the raw elemental power within them into any shape or size. However, since the forces balancing the universe are so upset, the White Guardian needs to recover the segments of the Key to stop the universe so that he can restore the balance. The White Guardian also warns the Doctor of the Black Guardian, who also wishes to obtain the Key to Time for his own purposes. In the final episode, the Black Guardian, disguised as the White Guardian, attempts to take the Key from the Doctor. However, the Doctor sees through the figure's charade and orders the segments of the Key to Time to once again become scattered across all of time and space, bar the sixth, which he reinstates as Princess Astra. Afterward, the Doctor decides to install a device called a randomiser into the TARDIS' navigation system for a period of time to make his following voyages unpredictable to evade the Black Guardian.

The six segments[edit]

  1. The first segment is disguised as a lump of Jethrik on the planet Ribos.
  2. The second is the planet Calufrax, shrunk to miniature size by the space-hopping pirate planet Zanak.
  3. The third is the Great Seal of Diplos, which has been stolen by a criminal of that planet.
  4. The fourth is part of a statue on the planet Tara.
  5. The fifth has been consumed by the squid Kroll, causing it to turn into a gigantic monster.
  6. The final segment is a female humanoid – Princess Astra.


Main cast[edit]

Guest Cast[edit]

Tom Baker continued his role as The Fourth Doctor, and saw the introduction of Romana played by Mary Tamm. This season was the only one to feature Tamm as the first incarnation of Romana, as the second incarnation, played by Lalla Ward, began her run in the first serial of the next season (Destiny of the Daleks).


Douglas Adams took over as script editor from Anthony Read for The Armageddon Factor. Season 16 consists of one long story arc encompassing six separate, linked stories.

StorySerialSerial titleEpisode titlesDirected byWritten byOriginal air dateProd.
UK viewers
(millions) [2]
981The Ribos Operation"Part One"George Spenton-FosterRobert Holmes2 September 1978 (1978-09-02)5A8.359
"Part Two"George Spenton-FosterRobert Holmes9 September 1978 (1978-09-09)5A8.1
"Part Three"George Spenton-FosterRobert Holmes16 September 1978 (1978-09-16)5A7.9
"Part Four"George Spenton-FosterRobert Holmes23 September 1978 (1978-09-23)5A8.267
The Doctor is recruited by the White Guardian to seek the six segments of the Key to Time. The quest for the first segment takes them to Ribos, a medieval planet that galactic confidence trickster Garron is trying to sell to the Graff Vynda-K.
992The Pirate Planet"Part One"Pennant RobertsDouglas Adams30 September 1978 (1978-09-30)5B9.161
"Part Two"Pennant RobertsDouglas Adams7 October 1978 (1978-10-07)5B7.4
"Part Three"Pennant RobertsDouglas Adams14 October 1978 (1978-10-14)5B8.264
"Part Four"Pennant RobertsDouglas Adams21 October 1978 (1978-10-21)5B8.464
The quest for the second segment takes them to the planet Zanak, which has been hollowed out and fitted with hyperspace engines, allowing its insane half-robot Captain to materialise it around other smaller planets and plunder their resources.
1003The Stones of Blood"Part One"Darrol BlakeDavid Fisher28 October 1978 (1978-10-28)5C8.6
"Part Two"Darrol BlakeDavid Fisher4 November 1978 (1978-11-04)5C6.6
"Part Three"Darrol BlakeDavid Fisher11 November 1978 (1978-11-11)5C9.3
"Part Four"Darrol BlakeDavid Fisher18 November 1978 (1978-11-18)5C7.667
The quest for the third segment takes them to Earth, where an ancient criminal who stole the segment disguises herself as the Celtic goddess Cailleach.
1014The Androids of Tara"Part One"Michael HayesDavid Fisher25 November 1978 (1978-11-25)5D9.5
"Part Two"Michael HayesDavid Fisher2 December 1978 (1978-12-02)5D10.165
"Part Three"Michael HayesDavid Fisher9 December 1978 (1978-12-09)5D8.9
"Part Four"Michael HayesDavid Fisher16 December 1978 (1978-12-16)5D9.066
The quest for the fourth segment takes them to the planet Tara. The Fourth Doctor and Romana find themselves embroiled in the political games of the planet Tara, where doubles, android or otherwise, complicate the coronation of Prince Reynart.
1025The Power of Kroll"Part One"Norman StewartRobert Holmes23 December 1978 (1978-12-23)5E6.5
"Part Two"Norman StewartRobert Holmes30 December 1978 (1978-12-30)5E12.4
"Part Three"Norman StewartRobert Holmes6 January 1979 (1979-01-06)5E8.9
"Part Four"Norman StewartRobert Holmes13 January 1979 (1979-01-13)5E9.963
The quest for the fifth segment takes them to the third moon of Delta Magna, caught in the middle of a dispute between the crew of a methane refinery and the natives (known as 'Swampies').
1036The Armageddon Factor"Part One"Michael HayesBob Baker and Dave Martin20 January 1979 (1979-01-20)5F7.565
"Part Two"Michael HayesBob Baker and Dave Martin27 January 1979 (1979-01-27)5F8.8
"Part Three"Michael HayesBob Baker and Dave Martin3 February 1979 (1979-02-03)5F7.8
"Part Four"Michael HayesBob Baker and Dave Martin10 February 1979 (1979-02-10)5F8.6
"Part Five"Michael HayesBob Baker and Dave Martin17 February 1979 (1979-02-17)5F8.6
"Part Six"Michael HayesBob Baker and Dave Martin24 February 1979 (1979-02-24)5F9.666
The quest for the sixth and final segment takes them to Atrios, a world at war with its planetary neighbour Zeos. But the Black Guardian is closing in.


The Key to Time was broadcast from 2 September 1978 to 24 February 1979.

DVD Releases[edit]

This entire season was released on 1 October 2002 with minimal restoration and commentaries and pop-up production notes in region 1, both as a box set as well as being available individually. A limited edition box set of 15,000 copies with full restoration, expanded extras and a fold out box design was released in region 2 on 24 September 2007. This limited edition version was later issued in a standard box for the 7 November 2007 region 4 release and the 3 March 2009 region 1 "Special Edition" release (region 1 serials were also available individually), and the 16 November 2009 non-limited region 2 re-release in a slipcase box.[3] There is also a region 4 version with the same fold out box design as the UK limited edition.

In print[edit]

Serial name Novelisation title Author First published
The Ribos Operation Doctor Who and the Ribos Operation Ian Marter 11 December 1979
The Pirate Planet The Pirate Planet James Goss 5 January 2017[4][5][6]
The Stones of Blood Doctor Who and the Stones of Blood Terrance Dicks 20 March 1980
The Androids of Tara Doctor Who and the Androids of Tara Terrance Dicks 24 April 1980
The Power of Kroll Doctor Who and the Power of Kroll Terrance Dicks 26 May 1980
The Armageddon Factor Doctor Who and the Armageddon Factor Terrance Dicks 26 June 1980


  1. ^ "Season 16". Doctor Who Classic Episode Guide. BBC. Retrieved 10 August 2007.
  2. ^ a b "Ratings Guide". Doctor Who News. Retrieved 27 December 2014.
  3. ^ "The Key to Time" DVD Feature Comparison. Retrieved 27 January 2014.
  4. ^ Adams, Douglas; Goss, James (5 January 2017). "Doctor Who: The Pirate Planet". BBC Digital. Retrieved 25 August 2016 – via Amazon.
  5. ^ "Gallifrey Guardian". Doctor Who Magazine. Tunbridge Wells: Panini UK Ltd (486): 7. April 2015.
  6. ^ Dave Golder (30 April 2015). "Doctor Who Pirate Planet Novelisation Announced". GamesRadar+.