The Key to Time

The Key to Time
Cover of the 2008 Region 2 DVD release
Starring	Tom Baker Mary Tamm John Leeson
Country of origin	United Kingdom
No. of episodes	26
Release
Original network	BBC One
Original release	2 September 1978 (1978-09-02) – 24 February 1979 (1979-02-24)

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. 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.

Synopsis

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

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.

Casting

See also: List of Doctor Who cast members

Main cast

• Tom Baker as the Fourth Doctor
• Mary Tamm as Romana
• John Leeson as Voice of K9

Guest Cast

• Valentine Dyall as the Black Guardian

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).

Serials

See also: List of Doctor Who episodes (1963–1989)

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.

Story	Serial	Serial title	Episode titles	Directed by	Written by	Original air date	Prod. code	UK viewers (millions)	AI
98	1	The Ribos Operation	"Part One"	George Spenton-Foster	Robert Holmes	2 September 1978 (1978-09-02)	5A	8.3	59
			"Part Two"	George Spenton-Foster	Robert Holmes	9 September 1978 (1978-09-09)	5A	8.1	—
			"Part Three"	George Spenton-Foster	Robert Holmes	16 September 1978 (1978-09-16)	5A	7.9	—
			"Part Four"	George Spenton-Foster	Robert Holmes	23 September 1978 (1978-09-23)	5A	8.2	67
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.
99	2	The Pirate Planet	"Part One"	Pennant Roberts	Douglas Adams	30 September 1978 (1978-09-30)	5B	9.1	61
			"Part Two"	Pennant Roberts	Douglas Adams	7 October 1978 (1978-10-07)	5B	7.4	—
			"Part Three"	Pennant Roberts	Douglas Adams	14 October 1978 (1978-10-14)	5B	8.2	64
			"Part Four"	Pennant Roberts	Douglas Adams	21 October 1978 (1978-10-21)	5B	8.4	64
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.
100	3	The Stones of Blood	"Part One"	Darrol Blake	David Fisher	28 October 1978 (1978-10-28)	5C	8.6	—
			"Part Two"	Darrol Blake	David Fisher	4 November 1978 (1978-11-04)	5C	6.6	—
			"Part Three"	Darrol Blake	David Fisher	11 November 1978 (1978-11-11)	5C	9.3	—
			"Part Four"	Darrol Blake	David Fisher	18 November 1978 (1978-11-18)	5C	7.6	67
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.
101	4	The Androids of Tara	"Part One"	Michael Hayes	David Fisher	25 November 1978 (1978-11-25)	5D	9.5	—
			"Part Two"	Michael Hayes	David Fisher	2 December 1978 (1978-12-02)	5D	10.1	65
			"Part Three"	Michael Hayes	David Fisher	9 December 1978 (1978-12-09)	5D	8.9	—
			"Part Four"	Michael Hayes	David Fisher	16 December 1978 (1978-12-16)	5D	9.0	66
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.
102	5	The Power of Kroll	"Part One"	Norman Stewart	Robert Holmes	23 December 1978 (1978-12-23)	5E	6.5	—
			"Part Two"	Norman Stewart	Robert Holmes	30 December 1978 (1978-12-30)	5E	12.4	—
			"Part Three"	Norman Stewart	Robert Holmes	6 January 1979 (1979-01-06)	5E	8.9	—
			"Part Four"	Norman Stewart	Robert Holmes	13 January 1979 (1979-01-13)	5E	9.9	63
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').
103	6	The Armageddon Factor	"Part One"	Michael Hayes	Bob Baker and Dave Martin	20 January 1979 (1979-01-20)	5F	7.5	65
			"Part Two"	Michael Hayes	Bob Baker and Dave Martin	27 January 1979 (1979-01-27)	5F	8.8	—
			"Part Three"	Michael Hayes	Bob Baker and Dave Martin	3 February 1979 (1979-02-03)	5F	7.8	—
			"Part Four"	Michael Hayes	Bob Baker and Dave Martin	10 February 1979 (1979-02-10)	5F	8.6	—
			"Part Five"	Michael Hayes	Bob Baker and Dave Martin	17 February 1979 (1979-02-17)	5F	8.6	—
			"Part Six"	Michael Hayes	Bob Baker and Dave Martin	24 February 1979 (1979-02-24)	5F	9.6	66
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.

Broadcast

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

DVD Releases

See also: List of Doctor Who home video releases

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. There is also a region 4 version with the same fold out box design as the UK limited edition.

In print

Main article: List of Doctor Who novelisations

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
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