Season 16

Season 16 of Doctor Who, also referred to as The Key to Time, ran from 2 September 1978 to 24 February 1979. It starred Tom Baker as the Fourth Doctor, Mary Tamm as Romana I and John Leeson as K9 Mark II. The season opened with The Ribos Operation and concluded with The Armageddon Factor.

Overview
It consisted of six serials comprised of twenty-six episodes. This season saw the introduction of the Black and White Guardians as well as the companion Romana I who became the first Time Lady companion since Susan. This season is sometimes colloquially known as The Key to Time season after the story arc involving the Key to Time. Although not the first season to consist of linked stories (Season 8 in 1971 was the first, as all the stories that year featured ), it was the first to be recognised as having a series-long arc. Although multi-serial arcs would occur again, such a full-season experiment wouldn't be attempted again until Season 23. The arc has a number of similarities to the Season 1 story The Keys of Marinus. The storyline was originally proposed for Season 15, but it required more planning.

Season 16 marked a triple milestone for Doctor Who: the hundredth story (The Stones of Blood), the five-hundredth episode (episode 1 of The Armageddon Factor) and the fifteenth anniversary of the first broadcast, on 23 November 1978.

A number of publicity photos for the season show Tom Baker sporting a very obvious bandage on his upper lip; this was due to his being bit by a dog shortly before filming for the season began. The resulting lip injury is visible to varying degrees throughout the season.

In 2002 (Region 1) it became the first Doctor Who season to be released to DVD in its entirety in a single box set; it remained the only "classic series" season to be available as a single set until the release of Season 23, The Trial of a Time Lord to DVD in 2008.

Tom Baker decided to leave by the end of this season, but he was persuaded to stay.

Cast

 * Doctor Who - Tom Baker
 * Romana I - Mary Tamm
 * K9 - John Leeson

Recurring

 * The Guardian - Cyril Luckham
 * The Guardian - Valentine Dyall

Guest

 * Garron - Iain Cuthbertson
 * Unstoffe - Nigel Plaskitt
 * Graff Vynda-K - Paul Seed
 * Sholakh - Robert Keegan
 * Binro - Timothy Bateson
 * Captain - Bruce Purchase
 * Mr. Fibuli - Andrew Robertson
 * Kimus - David Warwick
 * Mula - Primi Townsend
 * Nurse - Rosalind Lloyd
 * Professor Rumford - Beatrix Lehmann
 * Vivien Fay - Susan Engel
 * De Vries - Nicholas McArdle
 * Martha - Elaine Ives-Cameron
 * Megara Voices - Gerald Cross, David McAlister
 * Count Grendel - Peter Jeffrey
 * Zadek - Simon Lack
 * Prince Reynart - Neville Jason
 * Princess Strella - Mary Tamm
 * Farrah - Paul Lavers
 * Lamia - Lois Baxter
 * Till - Declan Mulholland
 * Archimandrite - Cyril Shaps
 * Thawn - Neil McCarthy
 * Fenner - Philip Madoc
 * Dugeen - John Leeson
 * Rohm-Dutt - Glyn Owen
 * Ranquin - John Abineri
 * Varlik - Carl Rigg
 * Skart - Frank Jarvis
 * Harg - Grahame Mallard
 * Marshal - John Woodvine
 * Princess Astra of Atrios - Lalla Ward
 * Merak - Ian Saynor
 * Shapp - Davyd Harries
 * The Shadow - William Squire
 * Pilot - Pat Gorman
 * Drax - Barry Jackson

Stories set before this season
The following stories are the known stories set between Season 15 finale The Invasion of Time and Season 16 opener The Ribos Operation:

Audio

 * The Sinestran Kill
 * Planet of the Drashigs
 * The Enchantress of Numbers
 * The False Guardian

to be completed

Novels

 * Tomb of Valdemar
 * The Shadow of Weng-Chiang
 * Fourth Doctor and Romana's involvement in Heart of TARDIS

Short Stories

 * X-Rani and the Ugly Mutants
 * Light Fantastic
 * Reluctant Warriors

Audios

 * Ferril's Folly
 * The Fourth Doctor and Romana I's involvement in Luna Romana

Comics

 * The Weapon

VHS releases

 * The Ribos Operation
 * The Pirate Planet
 * The Stones of Blood
 * The Androids of Tara
 * The Power of Kroll
 * The Armageddon Factor
 * The Tom Baker Years (excerpts from all stories)

DVD & Blu-ray releases
This entire season was released with minimal restoration and extras only in Region 1 as a box set or individually on 1 October 2002. A limited edition box set with full restoration and expanded extras was released in Region 2 on 24 September 2007. This limited edition set was later issued in Region 4 on 7 November 2007, in Region 1 on 3 March 2009 as a Special Edition release (these were also available individually), and in Region 2 on 16 November 2009 as a non-limited re-release.

Novels

 * Doctor Who and the Ribos Operation
 * The Pirate Planet
 * Doctor Who and the Stones of Blood
 * Doctor Who and the Androids of Tara
 * Doctor Who and the Power of Kroll
 * Doctor Who and the Armageddon Factor

Target Books was unable to come to an agreement with Douglas Adams to novelise his script, The Pirate Planet. It was finally adapted by BBC Books in 2017.