1966 (production)

March

 * 15 March - Pat Dunlop leaves working on The War Machines after partly completing a script for the first episode,due to the script work clashing with pre-existing work he had ongoing on another TV show. Ian Stuart Black takes over the writing duties for this story.
 * 25 March - "The Hall of Dolls" was recorded at Riverside Studios 1. (TCH 7)

April

 * April - The Ocean Liner, The Clock and The Evil Eye are all rejected by Gerry Davis.
 * In late April, the Doctor Who production office circulated a memo to writers outlining the proposed character of the Second Doctor, as well as suggestions on handling the first regeneration, which was initially compared to an LSD trip gone bad.

June

 * 17 June - Episode two of The War Machines was recorded at Riverside Studios 1. (TCH 8)

August

 * 6 August - The BBC announced to the press that William Hartnell was to leave the role of the first Doctor. Patrick Troughton signed a contract to play the second Doctor for 22 episodes.

September

 * 26 - 28 September - Model shots for The Power of the Daleks are filmed.

October

 * 8 October - Episode 4 of The Tenth Planet was taped, with the first scenes filmed being the regeneration from William Hartnell to Patrick Troughton.
 * 22 October - Episode 1 of The Power of the Daleks was taped; this was the first full episode featuring Patrick Troughton.

December

 * 12 December - The BBC Audience Research Dept. filed an Audience Research Report on The Power of the Daleks Episode 3, reporting that satisfaction in the episode ranked at 44% with response to new Doctor Patrick Troughton being particularly mixed.
 * 15 December - Patrick Troughton was interviewed in Radio Times.