Big Finish Productions is a British company that produces books and audio plays (released straight to compact disc and for download in MP3 and m4b format) based, primarily, on cult science fiction properties.[2][3][4] These include Doctor Who, the characters Judge Dredd and Strontium Dog from 2000 AD, Blake’s 7, Dark Shadows, Dracula, Terrahawks, Sapphire & Steel, Sherlock Holmes, Stargate, The Avengers, The Prisoner, and Torchwood.
(Taken from https://en.wikipedia.org/wiki/Big_Finish_Productions)