1 February 1975 13.6 million viewers tune in to the second episode of The Ark in Space, propelling Doctor Who to its highest rating and chart placing at that point, coming in as the fifth most-watched television programme of the week.
8 March 1975 The first appearance of Davros, the creator of the Daleks.
19 April 1975 The first appearance of the Cybermen since 1968’s The Invasion. The story is former script editor and Cybermen co-creator Gerry Davis’s final contribution to Doctor Who. Revenge of the Cybermen makes the first reference to the Cybermen’s vulnerability to gold.
23 April 1975 William Hartnell passes away, aged 67.
20 September 1975 After 98 episodes, Nicholas Courtney makes his final regular appearance as Brigadier Lethbridge-Stewart in Terror of the Zygons.
6 March 1976 The original TARDIS prop makes its final appearance after 13 years’ service to adventures in time and space. Years of being battered around studios and locations have taken their toll, resulting in the roof collapsing on Elisabeth Sladen during studio recording for The Seeds of Doom.
23 October 1976 Elisabeth Sladen makes her final regular appearance as Sarah Jane Smith – but Sarah’s story is in many ways only just beginning.
30 October 1976 Companionless for the very first time, the Doctor returns home to Gallifrey for The Deadly Assassin. The Master makes his first appearance since Frontier in Space, now played by Peter Pratt.
1 October 1977 A different kind of companion makes its debut, as robot dog K-9 whirrs into view for the first time.
18 July 1978 The cast and crew of The Stones of Blood enjoy a specially made birthday cake to celebrate making Doctor Who’s 100th adventure. The cake had originally been ordered as a prop for a scene in which the Doctor celebrates his 751st birthday, but the gag was never taped.
2 September 1978 The first appearance of Mary Tamm as Time Lady companion Romanad-voratrelundar – Romana for short. A season-long story arc begins as the Doctor, Romana and K-9 embark on the quest for the Key to Time.
30 September 1978 Douglas Adams contributes his first script to Doctor Who. His famous radio comedy, The Hitchhiker’s Guide to the Galaxy, first aired in March 1978.
30 April 1979 The Doctor Who cast and crew travel to Paris to record sequences for the upcoming City of Death, marking the series’ first location shoot abroad.
22 September 1979 Broadcast of Dalek creator Terry Nation’s final script contribution to Doctor Who – Destiny of the Daleks, Episode 4.
20 October 1979 With the BBC’s rival broadcaster ITV in the grip of industrial action that has taken it off the air, the final part of City of Death attracts Doctor Who’s highest-ever audience figure of 16.1 million viewers. It is a record that stands to this day.
10 December 1979 Continued industrial action by various technicians’ unions plagues filming on Shada, the final story of Season 17, forcing producer Graham Williams to officially abandon production. While it is doomed never to be transmitted, the story will eventually be released commercially as a VHS tape in 1992, with new linking material performed by Tom Baker, and reissued on DVD in 2013.
30 August 1980Doctor Who’s eighteenth season debuts, and with it a new version of the theme tune. Alterations have been made to the theme over the years, but the original mix created by Delia Derbyshire in 1963 has always been retained until now, as Peter Howell, of the BBC Radiophonic Workshop, completely reimagines the famous theme. To accompany the new arrangement, the title sequence abandons the ‘time tunnel’ effect for a background of stars, and features a brand new neon-style logo.
24 October 1980 A hastily arranged press conference is held to announce Tom Baker’s departure from Doctor Who at the end of Season 18. Although producer John Nathan-Turner is already in discussions with the actor who will be his new Doctor, Tom Baker’s teasing leads the press to speculate that ‘the new Doctor Who may even be a woman’.
5 November 1980All Creatures Great and Small star Peter Davison appears on BBC magazine programme Nationwide, confirming that he will be taking over the part of the Doctor from Tom Baker.
24 January 1981 K-9 leaves the series, along with Romana, but the tin dog will return to our screens later in the year.
21 February 1981 Two masterful first appearances in The Keeper of Traken. Geoffrey Beevers makes his debut as the emaciated form of the Master, but is replaced at the end of the story by Anthony Ainley, the fourth actor to play the renegade Time Lord.
21 March 1981 An end that spells a new beginning, as Tom Baker makes his final appearance as the Doctor, making way for Peter Davison’s brief debut as the Fifth Doctor. Davison’s credit in the closing titles is the last time an actor in the role is credited as ‘Doctor Who’ (rather than ‘The Doctor’) until 2005.
28 December 1981 The first Doctor Who spin-off is broadcast. K-9 and Company sees the return of Elisabeth Sladen to the Doctor Who universe as Sarah Jane Smith, joining K-9 Mark III for a spooky festive adventure. The hoped-for spin-off series fails to materialise – for now.
4 January 1982 After the longest-ever gap between seasons of Doctor Who, a new era begins with Castrovalva Part 1, marking Peter Davison’s first full episode as the Doctor. After eighteen years occupying a traditional Saturday teatime slot in the schedules, Doctor Who moves through time and space to a twice-weekly broadcast on Monday and Tuesday evenings at 6.40pm. This episode also marks the first use of a pre-titles scene, reprising the regeneration scene from the end of Logopolis Part 4.
22 February 1982 Millions of Doctor Who viewers watch in horror as the sonic screwdriver makes its final appearance, an old friend blasted to pieces by a Terileptil’s gun.
8 March 1982 In a shock cliff-hanger ending, Earthshock sees the Cybermen make their first full appearance in eight years.
16 March 1982 Companion Adric, played by Matthew Waterhouse, is killed off. In a break with tradition, the closing credits run with no music for the one and only time in the series’ history.
1 February 1983Mawdryn Undead sees Nicholas Courtney make his first appearance as the Brigadier in eight years.
28 July 1983 Following a press conference, the BBC lunchtime news reveals that Peter Davison will depart the role of the Doctor at the close of the 21st season. His successor has been cast, but is yet to be revealed to the world at large.
19 August 1983 Popular television actor Colin Baker is announced as the sixth actor to play the Doctor. The announcement is made at a press conference in which the actor is joined by Nicola Bryant, who will play the Doctor’s latest companion, Peri Brown.
October 1983Revenge of the Cybermen becomes the first Doctor Who story to be released on home video on VHS, Betamax and Video 2000 formats.
23 November 1983Doctor Who’s twentieth anniversary, and the first broadcast of the anniversary special The Five Doctors takes place – in the USA.