They are produced by Big Finish Productions and star one or more of the original actors to play the Doctor on television in the classic era of the programme.
Though the programme had been put on indefinite hiatus in 1989 (and despite the failed revival attempt with the 1996 TV movie), the BBC still published, as well as gave non-exclusive licenses to other companies, Doctor Who stories through various mediums such as novels and comics.
[3][4] This eventually transitioned into a license to produce original audio dramas featuring the past Doctors, with The Sirens of Time being the first story to be released in July 1999.
[8] Since then, every televised companion has reprised their role in Big Finish (with the exception of Jackie Lane's Dodo Chaplet).
[11] The releases have also been compared to fanfiction, in the way they try to "correct perceived transgressions",[12] focus on and deepen the characterisation and emotions of characters,[13] and revitalise the earlier dynamics of some villians[14] while also recontexualising their motivations.
[15] On a more neutral level, they have been characterised as focusing more on the 'interpersonal' than the 'epic'; that instead of homages, they serve as supplements to the story, improving and emphasising other parts of the plot.
[16] Though the BBC has not echoed the sentiment, executive producer Nicholas Briggs considers the audios to be completely canonical.
The following list mentions the guest actors who have never appeared as a main character in any year, but have appeared as allies or enemies of the Doctor various times in the Main Range or in other mediums, listed alphabetically by character's last name (or only names when the last name is unknown or does not exist): In May 2020, Big Finish announced that the Main Range would conclude with its 275th release, to be replaced with regular releases of each Doctor in their own boxsets throughout the year from January 2022.