The series was originally released as direct-to-video films produced by BBV Productions, with four of its five instalments being released during the period of Doctor Who's cancellation.
In 2020, Arcbeatle Press made a publishing partnership with BBV and "revived" the series, starting with the release of Shadows of Doubt. The next year, BBV Productions themselves released two volume's worth of live-action P.R.O.B.E. shorts, the P.R.O.B.E. Case Files.
Unlike UNIT, P.R.O.B.E. was a small-scale organisation answerable to the British government — and its purpose was to investigate the strange and the out of the ordinary, rather than merely the extraterrestrial. Liz's only colleague in the original films was assistant Louise Bayliss, who was transferred by minister Brian Rutherford in a bid to have the organisation closed. However, permission was required from Liz's ministry liaison and later lover Patsy Haggard, who refused to do so and frequently went out of her way to assist Liz. Although mention of the Doctor and the events of season 7 was forbidden due to licensing restrictions, a number of Doctor Who actors featured in the series in new roles, notably Jon Pertwee, Peter Davison, Colin Baker and Sylvester McCoy, as well as Louise Jameson in the recurring role of Patsy.
The first four films were written by Mark Gatiss and directed by Bill Baggs. After Caroline John's death in 2012, the role of Liz was recast and given to Hazel Burrows in When to Die, a tribute to John written and directed by Baggs. Jameson did not return as Patsy, who was instead played by Georgette Ellison. The film also introduced two new members of the team: the eccentric technician Giles and the K9-esque portable computer Box. Later P.R.O.B.E. media starting from Shadows of Doubt featured a new P.R.O.B.E. team which had formed around Giles and Box, including Archie MacTavish, Az, Tasha Williams, Agamya and the alien refugee Maxie Masters. Liz (now Liz Haggard) was presented as retired and living in Spain with her now-wife Patsy, though she kept in contact with the new team.