It's Maria and Luke's first day at Park Vale Comprehensive, and they soon befriend charming troublemaker Clyde Langer. But not everything seems right: the food in the cafeteria has gone off, there's a mysterious new technology wing, and some of the teachers have developed an issue with flatulence. When a sudden power cut in the area impacts even non-electrical energy sources, Sarah Jane becomes determined to investigate. With the aid of her young friends, she discovers that schools all over the world have been infiltrated by the Slitheen, who intend to wreak their vengeance on the entire planet.

When Doctor Who executive producer Russell T Davies pitched the idea of a series focussing on Sarah Jane Smith to Children's BBC, he piqued their interest with a single story concept: Sarah Jane versus the Slitheen. The Slitheen had been introduced in 2005's Aliens Of London / World War Three, part of the first season of the relaunched Doctor Who, and they held a particular appeal for younger viewers. As such, it was felt that they were an ideal nemesis to appear in what became The Sarah Jane Adventures, given that it was being designed to skew towards a more juvenile audience than Doctor Who itself. Although the introductory special, Invasion Of The Bane, saw Sarah Jane and her friends tackling a brand-new alien threat, Davies believed that the Slitheen were the perfect attraction for the opening story of the first full season of The Sarah Jane Adventures, cementing the new programme's connection with Doctor Who.

The writer assigned to the season premiere was Gareth Roberts, Davies' collaborator on Invasion Of The Bane. In addition to the inclusion of the Slitheen, Roberts was also asked to introduce a new regular character in the form of Clyde Langer. Clyde had been developed by Davies as a replacement for Kelsey Hooper, whom Roberts had created for the special. Although Kelsey's attitude and cynicism made an appealing contrast to the other young characters -- Maria Jackson and Luke Smith -- it was felt that The Sarah Jane Adventures could benefit from a second male protagonist. As such, Kelsey actress Porsha Lawrence-Mavour was not brought back for the full season, and Clyde was devised to inherit many of Kelsey's basic traits. Some reports also suggested that Lawrence-Mavour had been a disruptive presence on set.

Cast as Clyde was Daniel Anthony, who had appeared in multiple episodes of EastEnders and Doctors

Roberts' script -- eventually titled Revenge Of The Slitheen -- was part of the season's first recording block, and was paired with the second story, Eye Of The Gorgon. The director was Alice Troughton, who had recently completed Small Worlds and Out Of Time for Doctor Who's other spin-off series, Torchwood. Cast as Clyde was Daniel Anthony, an actor who had appeared in multiple episodes of EastEnders and Doctors. Unlike his co-stars Yasmin Paige (born in 1991) and Tommy Knight (born in 1993), Anthony was already an adult -- in fact, he was just a few months shy of his twentieth birthday. As such, he was not subject to British laws limiting the hours per day during which child actors were permitted to work, thereby providing additional flexibility when it came to the recording schedule.

Meanwhile, the programme's production team had been rounded out with the addition of Matthew Bouch. He would take over as producer on an ongoing basis, after Susie Liggat had served in that capacity on Invasion Of The Bane. Bouch had been a script editor or script executive on programmes such as Holby City, EastEnders and the telefilm remake of A For Andromeda, and he had also co-produced The Legend Of The Tamworth Two.

Filming for Block One began on April 16th, 2007, but the first two weeks were almost exclusively devoted to Eye Of The Gorgon. This schedule was designed to help establish the cast dynamic before embarking on the crucial premiere episodes. The only exception was a scene in Maria's bedroom, taped at the programme's studio facilities in Upper Boat on April 19th. The first full day of filming on Revenge Of The Slitheen was April 30th. Work began on Clinton Road in Penarth for material on Bannerman Road, before moving to Cardiff where Whitchurch High School posed as St Cheldon's Comprehensive. Production then returned to Clinton Road from May 1st to 3rd.

Except for its new wing, Park Vale Comprehensive was really Cardiff High School, the venue for filming on May 4th and 7th. The next location was an old factory at the Johnsey Estates, part of the Mamhilad Park Industrial Estate in Pontypool, for sequences in the Slitheen capacitor room. Recording there took place from May 8th to 10th, with part of the latter day also reserved for the American news broadcast, which was taped at BBC Broadcasting House in Cardiff. For the latter, Lachele Carl reprised the role of the news anchor first seen in Aliens Of London / World War Three, who had reappeared in several subsequent Doctor Who adventures. The scenes in Park Vale's new wing were completed at the Cardiff campus of Coleg Morgannwg starting on May 11th, and continuing after the weekend from the 14th to the 16th.

May 17th and 18th were split between sequences in Sarah Jane's attic at Upper Boat, and those at Coldfire Construction, which was actually Unit A5 on Severn Road in Pontypridd. Additional attic material was recorded at Upper Boat on the 21st. The scene of people watching the sun was performed on May 22nd along Ffordd-Y-Gollen in Tonteg. Work wrapped up on the 23rd, first with exterior shots of Coldfire Construction -- again at Unit A5 -- and then a variety of inserts at Upper Boat. The latter saw the first use of an enhanced version of the Mr Smith prop. For Invasion Of The Bane, the computer had emerged from the wall by means of a hand-crank, which proved to be a slow and arduous process; this was now made much more efficient by the introduction of a motor.

In editing, however, it was found that both episodes of Revenge Of The Slitheen were too short, and so additional material was written to fill out the runtime. All of this footage was set on Bannerman Road, so that Troughton could record the new scenes on Clinton Road on June 25th, during work on the season finale, The Lost Boy. Graphics elements for Mr Smith were also captured on July 2nd at Upper Boat. Oddly, alongside a gallery of other monsters from Doctor Who and Invasion Of The Bane, Mr Smith displayed an image of Abaddon from End Of Days, the final episode of Torchwood's first season -- despite the fact that the production team had decided not to refer to the other spin-off in The Sarah Jane Adventures, given the significant discrepancy in the two programmes' target demographics.

On August 14th, the BBC announced that episodes of The Sarah Jane Adventures would debut on the CBBC digital channel. An exception was confirmed on September 7th, when it was revealed that the season premiere would first air on BBC One. After this, episodes would settle down into a regular pattern of being repeated on BBC One seven days after their CBBC broadcast. Consequently, Episode One of Revenge Of The Slitheen aired on BBC One on Monday, September 24th, followed immediately afterwards by Episode Two on CBBC. Episode Two then received a terrestrial transmission on BBC One on October 1st, just before Eye Of The Gorgon Episode One debuted on CBBC. The strategy was successful, with the first installment bringing BBC One its largest audience so far that year in the timeslot, and CBBC witnessing its best ratings of 2007 to that point for the concluding episode.

• Doctor Who Magazine Special Edition #23, 24th December 2009, “Episode 1.1/1.2: Revenge Of The Slitheen” by Andrew Pixley, Panini Publishing Ltd.