John also played Liz Shaw in a series of straight-to-video stories produced by BBV under the umbrella title of P.R.O.B.E., in which the character works with a paranormal investigation organisation not unlike UNIT, called the "Preternatural Research Bureau". John later returned as Liz appearing in five Big Finish audio stories narrated by the character: The Blue Tooth (2007), Shadow of the Past (2010), The Sentinels of the New Dawn (2011), Binary (2012), and The Last Post (2012). The latter introduces Rowana Cooper as Liz's mother, Emily, and the planned sequel was not finished due to John's death in June 2012, although Cooper reappears as Emily Shaw in the audio "The Cloisters of Terror" when she assists the Fourth Doctor and Leela in investigating a mystery at her college.