"The Zero Imperative" (1994) marked a new departure for BBV. Although stuffed to the gills with ex-"Doctor Who" guest stars, only one of them was actually playing the same character: the story was built around Caroline John's Dr Elizabeth Shaw, the Doctor's companion in the seventh season of "Doctor Who", now depicted as an investigator for PROBE (the "Preternatural Research Bureau"). The PROBE series ran for an additional three stories; all four were written by Mark Gatiss, who later found more widespread fame as a member of the League of Gentlemen. The potentially-confusing mixture of Caroline John reprising her "Doctor Who" role with other recognisable "Who" stars playing different characters worked against the series, as did the way that Liz Shaw often seemed to be herself a different character from the "Doctor Who" original. (The latter problem may have been exacerbated by the fact that, although BBV had obtained permission to use Liz Shaw, they had no rights relating to "Doctor Who" itself - which meant that no explicit reference could be made to any other aspect of "Doctor Who", including the events of the stories in which Liz had appeared.)