Adventures in a Pocket Universe, also known as The Mistress, was a series of audio dramas released by BBV Productions under their "Audio Adventures in Time and Space" banner. The two audio dramas featured John Leeson and Lalla Ward as K9 and his Mistress.
The first two audio stories in the series, The Choice and The Search, were intended to form a sequel to Warriors' Gate, in which Romana II and K9 were left in E-Space. Though BBV Productions was able to secure the original actors for those two roles and the rights to K9 from Bob Baker and Dave Martin, they had no rights to the character of Romana or the concept of E-Space, so in the audios, K9 instead travels with a woman known simply as "the Mistress" in Ecto-Space.
Zoltán Déry also submitted a script for a third episode, The Liberator, to BBV. It was ultimately unproduced, but interested BBV sufficiently for them to commission an unrelated script from Déry which became The Green Man. (REF: Downtime – The Lost Years of Doctor Who)
In April 2022, The Choice was novelised as part of the Novelisations in Time & Space range. However, due to the rights agreement for K9 apparently not having covered adaptions in other media, K9 was removed from the plot and the Mistress was instead given a new robotic companion, a female bionic ferret called B.E.S.. Notably, this release employed the series name The Mistress instead of Adventures in a Pocket Universe. The original name was returned to the very next month for B.E.S. Begins, an audio release which related B.E.S.'s first meeting with the Mistress.
|1.1||The Choice||Nigel Fairs||K9, the Mistress||June 1999||The Choice|
|1.2||The Search||Mark Duncan||September 1999||N/A|
|1.3||B.E.S. Begins||James Mulholland||The Mistress, B.E.S.||24 May 2022|