Sarah Jane and her friends investigate what they expect to be a meteorite, but which turns out to be a crashed Judoon prisoner transport. It was carrying an intergalactic serial killer named Androvax -- a Veil, capable of inhabiting the bodies of others. Sarah Jane forges an uneasy alliance with Judoon Captain Tybo in an effort to recapture Androvax, but she falls prey to the Veil herself. Now in possession of all of Sarah Jane's knowledge and weapons, Androvax sets his sights on Genetec Systems -- whose nanobot technology will help him escape the Earth, or destroy it in trying.

On November 25th, 2008, the BBC publicly confirmed that there would be a third season of The Sarah Jane Adventures, although the production team had been planning for the possibility since late 2007. Nonetheless, they found themselves faced with some difficult decisions, as the programme's budget -- already cut for its second season -- was slashed even further. In October, some consideration had been given to an offer by Jane Tranter, the BBC's Controller of Fiction, to move the original broadcast of each episode to Sunday afternoons on BBC One, with repeats on the CBBC digital channel -- effectively, the reverse of the programme's normal transmission schedule -- with the budget restored to the level of the first season. However, in order to free up the funds, there would have to be a one-year hiatus before the third season could go before the cameras, and executive producer Russell T Davies was wary of such a long absence from the airwaves.

In the end, it was decided to accommodate the decreased budget principally by moving to a new recording model. For its first two seasons, The Sarah Jane Adventures had been divided into blocks which typically consisted of two stories -- four episodes -- all made by a single director. Now, however, each serial would form its own block, with two directors alternating throughout the season; this would allow greater economy in the overall shooting schedule. The director for the first, third and fifth stories of the third season would be Joss Agnew, who had made The Last Sontaran and The Mark Of The Berserker during 2008. He would also shoot the charity mini-episode From Raxacoricofallapatorius With Love... shortly before work began on the new run.

Russell T Davies and Julie Gardner were joined as executive producers by Piers Wenger, Head of Drama for BBC Wales

During 2009, Doctor Who would be undergoing a comprehensive turnover both in front of and behind the camera, with Davies, star David Tennant, and executive producer Julie Gardner all leaving. By contrast, The Sarah Jane Adventures would enjoy a period of relative stability, as both Davies and Gardner were retaining their status as executive producers despite their plan to relocate to Los Angeles. The pair would, however, be joined by Piers Wenger now that he had succeeded Gardner as Head of Drama for BBC Wales; he was taking up the same post on Doctor Who.

Phil Ford would continue to be the lead writer for The Sarah Jane Adventures, and the season premiere would number amongst his 2009 assignments. Sticking to the established format, it would grab viewers by pitting Sarah Jane against a familiar monster from Doctor Who. After appearances by the Slitheen in 2007's Revenge Of The Slitheen and a Sontaran in 2008's The Last Sontaran, Davies suggested bringing back the Judoon, the rhinoceros-like intergalactic policemen he had created for the 2007 Doctor Who season premiere, Smith And Jones. This was not the first time they had been considered for The Sarah Jane Adventures; their appearance had also been mooted for “The Trial Of Sarah Jane Smith”, an early candidate for the slot ultimately occupied by The Last Sontaran.

Since Smith And Jones had established that the Judoon were not normally permitted on Earth, this prompted the idea of a lone, stranded Judoon. From there, Ford developed the notion that the real villain of the piece would be an alien criminal whom the Judoon was transporting: Androvax the Veil. Androvax's ability to possess people was inspired by Elisabeth Sladen's interest in playing an evil version of Sarah Jane, which she had suggested during the production of the 2008 season.

Around the same time, Ford was writing an animated Doctor Who adventure called Dreamland featuring the Tenth Doctor, which would be broadcast in late 2009. This script wove together elements of UFO lore such as the alleged crash of an alien spaceship near Roswell, New Mexico in 1947, and the existence of a secret American air force base at Area 51 in Nevada which was believed to house recovered extraterrestrial technology. Ford saw an opportunity to tie together these branches of the Doctor Who family, by having Androvax steal the plans of the Roswell ship to aid in his escape from Earth. Ford's season premiere script was eventually known as Prisoner Of The Judoon.

On April 10th, Elisabeth Sladen and Tommy Knight recorded cameo appearances for the final Tenth Doctor story

Castmembers from The Sarah Jane Adventures were involved in two key pieces of filming prior to the start of work on the show's third season in early 2009. First, all the regular castmembers -- plus John Leeson as the voice of K·9 -- were involved with the charity mini-episode From Raxacoricofallapatorius With Love... on February 19th. Then, on April 10th, Sladen and Tommy Knight were at Clinton Road in Penarth -- the usual venue for scenes on Bannerman Road -- to record cameo appearances in The End Of Time, the final story of Tennant's tenure as the Tenth Doctor.

Recording for The Sarah Jane Adventures resumed on April 20th, with work getting under way on the set for Sarah Jane's attic at the programme's regular studio facilities in Upper Boat. The rest of the week -- from the 21st to the 24th -- was spent at the Linea Building in Cardiff's St Mellons Business Park, which served as the exterior and most of the interior of Genetec Systems. The security office, the airtight lab and the room where Tybo became trapped were actually located in the Biomedical Science Building at Cardiff University, where cameras were rolling on April 27th. On the 28th, Agnew's team visited the Billy Banks housing estate in Penarth; this disused development was scheduled for demolition, and it was therefore ideal to represent the Brindley Chase estate. April 29th brought cast and crew back to the familiar venue of Clinton Road.

April 30th was originally meant to be another day spent at the Billy Banks estate, but heavy rains made this impossible. Instead, a number of scenes were rewritten so that they could be recorded at the All Saints Church Hall in Penarth. With the skies having cleared, work on May 1st took in a variety of Penarth locations: the conclusion of the footage begun the previous day at All Saints, Luke tricking Tybo at the Billy Banks Estate, Tybo seizing the police vehicle at Royal Close and driving it along that street and Paget Road, and the material with the speeder at the corner of Arcot Street and High Street. Principal photography concluded at Upper Boat on May 4th, for scenes in the Chandra home and aboard Androvax's spacecraft. Agnew then captured pick-up shots at Upper Boat on May 5th and 22nd.

It was ultimately agreed that the transmission pattern for The Sarah Jane Adventures would change for its third season. Not only would all of the episodes now premiere on BBC One before being repeated on CBBC, but the programme would also move to a twice-weekly schedule. This meant that an entire story would now unfold over the course of a Thursday and Friday afternoon, rather than requiring viewers to wait a week between story halves. For the first time, The Sarah Jane Adventures would also be broadcast in both standard and high definition.

Furthermore, it was decided to adapt a cinema trailer made for the show's second season to act as an introduction to each episode. Recorded at Clinton Road on July 15th by producer Nikki Wilson, it saw Daniel Anthony, in character as Clyde Langer, speaking to the camera to explain the premise of The Sarah Jane Adventures, before meeting up with Sarah Jane and Luke. His dialogue also firmly established Sarah Jane's address as 13 Bannerman Road, after her house number had appeared inconsistently during the programme's early episodes. It was this introduction which greeted viewers when Prisoner Of The Judoon Episode One heralded the start of the new season on October 15th.

• Doctor Who Magazine Special Edition #28, 13th July 2011, “Episodes 3.1/3.2: Prisoner Of The Judoon” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Writer's Tale: The Final Chapter by Russell T Davies and Benjamin Cook (2010), BBC Books, ISBN 978 1 846 07861 3.