A surviving Slitheen, masquerading as the mayor of Cardiff, plans to construct a nuclear reactor in order to tap into the power of the time rift running through the heart of the city. The Doctor, Rose and Jack set out to stop her and turn her over to the law on Raxacoricofallapatorius. But the Doctor is confronted with a difficult choice when it is revealed that the Slitheen faces a death sentence on her homeworld.

Unlike the other stories which would comprise Doctor Who's first year back on the air, the eleventh episode of the new season was not described in any detail in executive producer Russell T Davies' pitch document from the autumn of 2003. Davies simply indicated that this episode (given the heading “The New Team” due to the introduction of Jax -- later Jack Harkness -- in the previous episode) would be a “small-scale”, character-oriented adventure. Davies knew that the season's climactic two-part serial would be a major drain on the programme's budget, and so planned the preceding story as a cost-saving measure.

Originally, Davies hoped to woo Paul Abbott (creator of TV series such as Touching Evil and Linda Green) to write the episode, but Abbott proved too busy. Instead, Davies decided to tackle the story himself, and briefly considered calling the adventure “Pompeii”, setting the action around the cataclysmic eruption of Mount Vesuvius in AD 79. During the production of Aliens Of London / World War III in August 2004, however, Davies was impressed by the performance of Annette Badland as Blon Fel Fotch Pasameer-Day Slitheen, the alien masquerading as Margaret Blaine. After ensuring that Badland would be available in early 2005, Davies therefore decided to include the character in a new story which would examine the moral repercussions of the Doctor's deeds -- particularly in the context of capital punishment, to which Davies was personally opposed. Davies also took the opportunity to set an episode in modern-day Cardiff, the production home of the new Doctor Who series, by drawing on the plot point of the time rift established in The Unquiet Dead earlier in the season.

Davies' story was originally called “Dining With Monsters”, and subsequently became Boom Town. Initial planning paired the story with the season's final two episodes -- Bad Wolf / The Parting Of The Ways -- to form the fifth production block. For logistical reasons, however, Boom Town eventually comprised Block Five by itself, despite the fact that all three episodes would be directed by Joe Ahearne. Ahearne had already handled the third recording block (Dalek and Father's Day) in October and November 2004.

Work on Boom Town got under way on January 19th, 2005, with material involving the Doctor and Blon's dinner taped in and around Bistro 10 on Mermaid Quay in Cardiff Bay. Both February 1st and 2nd were then split between Cardiff's Glamorgan House (posing as the Town Hall) and Mermaid Quay (for sceness in the square, actually Plas Roald Dahl). The 3rd was spent in the studio at Unit Q2 in Newport, for segments in the TARDIS. Rose's mention of having visited the planet Justicia replaced what was originally a reference to Grajick Major. It served to link the televised series to the planned line of novels from BBC Books featuring the Ninth Doctor; Justicia appeared in Stephen Cole's Monsters Inside.

More Town Hall sequences were taped at Glamorgan House on February 4th, followed by another day on the TARDIS set in Newport on the 5th. The 8th saw cast and crew return to Mermaid Quay, including the Bosphorus Restaurant for the scene where the Doctor sees “Margaret's” photo in the newspaper (a sequence which was originally meant to transpire outside a bar). After another day recording TARDIS material on February 10th, the 11th and 14th were once again spent at Glamorgan House. The 15th began with Mickey's arrival at Cardiff Railway Station, before the final footage was captured on Mermaid Quay. Finally, insert shots were recorded at Unit Q2 on February 18th.

• Outpost Gallifrey: New Doctor Who Series News Page, edited by Shaun Lyon.
• Doctor Who Magazine Special Edition #11, 31st August 2005, “Fact File: Boom Town” by Andrew Pixley, Panini Publishing Ltd.