A cold opening (or pre-title sequence) was the scene of a story that appeared prior to the title sequence.
With some exceptions, cold openings were not featured in the classic series of Doctor Who, which ran from 1963 to 1989. A cold opening was, however, featured in the one-off TV movie from 1996. Cold openings would go on to become a permanent instalment of the new series of Doctor Who from 2005 to 2017, again with only a few exceptions, until being completely abandoned during 2018's series 11. This would later prove to be temporary, as cold openings were promptly reintroduced in 2020's series 12, but as an on-and-off feature. In series 13 they were brought back for all episodes, with Survivors of the Flux standing out as the only exception.
Torchwood series 1 and series 2 featured cold openings, as did The Sarah Jane Adventures and Class.
A Girl's Best Friend, the first and only story of K9 and Company, did not feature a cold opening. Similarly, no episodes of K9 featured cold openings either.
Exceptions to the above boundaries
In the classic series, just four stories featured a cold opening. 1982's Castrovalva, the debut story of Peter Davison as the Fifth Doctor, was the first, showing a recap of the end of Logopolis. The twentieth anniversary special, 1983's The Five Doctors, was the second, showing the First Doctor's speech from the end of The Dalek Invasion of Earth. These two stories were followed by 1987's Time and the Rani, the debut of Sylvester McCoy as the Seventh Doctor, and 1988's Remembrance of the Daleks, both of which featured a newly-made sequence to open the story. The animated reconstructions of 1966's The Power of the Daleks, 1967's The Macra Terror, as well as the incomplete Douglas Adams story Shada, also featured cold openings.
In the new series, the majority of exceptions were series premieres. Rose, Smith and Jones and Partners in Crime, which were the series premieres of series 1, 3 and 4 respectively, all did not feature cold openings. The fiftieth anniversary story, 2013's The Day of the Doctor, did not feature a cold opening, instead beginning with a slightly modified version of the title sequence from the first Doctor Who television story, 1963's An Unearthly Child, in widescreen.
Although returning in series 12 after their absence in series 11, only four episodes featured cold openings: Spyfall: Part One, Can You Hear Me?, The Haunting of Villa Diodati and Ascension of the Cybermen. Cold openings became became standard again in series 13, with the only exception being Survivors of the Flux.
The pilot episode of Torchwood, Everything Changes, was the only exception to the format for the first two series by not featuring a cold opening. Similarly, the pilot story of The Sarah Jane Adventures, Invasion of the Bane was also the only story of the show not to feature a cold opening.