In the seventeenth century, the Doctor, Amy and Rory find themselves aboard the Fancy, a pirate ship captained by Henry Avery. The vessel has been becalmed for days, marooned in waters that seem to be haunted by a Siren: a beautiful but demonic woman who stalks the sick and injured. She sings a mournful, bewitching melody, and her arrival is foreshadowed by a livid black spot which appears on the victim's skin. Soon, both Rory and Avery's stowaway son, Toby, are marked as the Siren's next targets. It falls to the Doctor and the reluctant Captain to unearth the creature's true nature, before it's too late.

Interest in the pirate genre was enjoying a resurgence during the early years of the twenty-first century, largely thanks to the 2003 blockbuster Pirates Of The Caribbean: The Curse Of The Black Pearl. Doctor Who had not attempted such a story since The Smugglers in 1966, so executive producer Steven Moffat decided that Season Thirty-Two should feature an adventure steeped in pirate lore. To develop the script, he approached Steve Thompson, a former maths teacher who had become a writer while raising his children. Thompson was working with Moffat on the Arthur Conan Doyle adaptation Sherlock, and had made no secret of his interest in contributing to Doctor Who.

The area of the United Kingdom most associated with piracy was Cornwall; indeed, it had also been the setting for The Smugglers. This prompted Thompson's recollection of a popular Cornish legend about the Mermaid of Zennor, which dated from at least the fifteenth century. It told of a mermaid with a beautiful singing voice who tempted a human man to come live with her under the sea, and was associated with an ancient chair bearing a carving of a mermaid, located in St Senara's Church in Zennor. The Mermaid of Zennor reminded Thompson of the Sirens, half-human women in Greek mythology whose song lured sailors to their deaths. Having appeared without description in Homer's Odyssey, the Ancient Greeks initially imagined them as part-bird creatures before a mermaid-like half-fish representation became predominant.

Henry Avery had been prominently referenced in 1966's The Smugglers

For a real-life pirate to anchor his narrative, Thompson chose Henry Avery -- also spelt “Every” or “Evory” -- who had been prominently referenced in The Smugglers. Active in the late seventeenth century, the so-called Arch Pirate had been a member of the Royal Navy before joining the Spanish slave trader Charles II as first mate. Following a mutiny over withheld wages, Avery became captain of the rechristened Fancy. He was a pirate for two years, and most famously plundered an immense fortune from the Ganj-i-sawai, flagship of Aurangzeb, emperor of the Mughals in India. Having vanished with a portion of his newfound wealth, Avery's final fate was unknown. This appealed to Thompson, who felt that it gave him carte blanche to tell the rest of Avery's story.

Thompson began work on his adventure in March 2010. He initially took a budget-conscious approach, with the action set around the Cornish coast. In this version, Captain Avery was searching for his missing wife, who had been kidnapped by the Siren. The Doctor eventually helped track the creature to a mine, where it was killed. When it was realised that there were sufficient funds available to set much of the story at sea, the Cornish setting was dropped in favour of the Fancy. Thompson now introduced a militia which boarded the ship, only for its corrupt lieutenant to force the crew to help him seek buried treasure on a nearby island. These characters were omitted when it was found that they over-complicated the storyline. It was only at this stage that the Siren became a medical interface, while early drafts also positioned Amy as her target, rather than Rory.

Thompson's story was known as both “Siren” and “The Siren”. It was planned to be the second episode of the latter half of Season Thirty-Two, and the ninth episode overall. However, towards the end of 2010, Moffat decided to rebalance the running order, with “Siren” moving into the first half of the run as episode three. The Doctor's Wife was pushed from third to fourth, while the original episode four, Night Terrors, would take the slot vacated by “Siren”. Moffat felt that the relatively lighthearted pirate narrative would be an effective counterpoint to the more intense adventures which otherwise made up the year's opening salvo.

Care was taken to ensure that Hugh Bonneville would not resemble Captain Jack Sparrow from Pirates Of The Caribbean

“Siren” was made as the only episode of Season Thirty-Two's fifth production block -- officially labelled “Block Four-B” -- under director Jeremy Webb. Cast as Captain Avery was Hugh Bonneville, who had recently garnered notice for his leading role in the period drama Downton Abbey. To avoid giving the impression that “Siren” was a pastiche, care was taken to ensure that Bonneville would not resemble Johnny Depp's iconic Captain Jack Sparrow from the Pirates Of The Caribbean franchise. A more unusual casting choice was Lily Cole as the Siren. Best known as one of the preceding decade's foremost supermodels, Cole had recently begun moving into acting, taking roles in films such as St Trinians and The Imaginarium Of Doctor Parnassus. Meanwhile, a late deletion from Thompson's script was the idea that the Siren would appear to Toby Avery in the form of a young girl, giving the Doctor a clue as to the entity's true nature.

The first material recorded for “Siren” was overseen by Julian Simpson, who had recently completed The Rebel Flesh / The Almost People. This was the footage of the “Eye Patch Woman”, recorded at Fillcare in Pontyclun on January 27th, 2011. Webb took over on January 28th, when scenes in the Fancy's store and magazine were recorded at Doctor Who's regular studio facilities in Upper Boat. It was back to the studio after the weekend, with January 31st spent on TARDIS sequences. The only location filming for “Siren” took place aboard the Phoenix Of Dell Quay, a two-masted brigantine berthed at the harbour in Charlestown, Cornwall. Material on the deck of the Fancy and in the rowboat was recorded there from February 1st to 3rd. Friday the 4th was a day off, as the cast and crew returned to Wales from Cornwall. The week ended on February 5th, on the set for the captain's cabin at Upper Boat.

The remainder of the production was confined to the studio. After another rest day on Sunday the 6th, February 7th and 8th dealt with material in the magazine and the below-decks area. Sequences in the hold were also filmed on the first day, while the second day saw the recording of the episode's prequel, in which Avery wrote ominously in his journal. Somewhat ahistorically, the prequel set the events of “Siren” in 1699; in reality, Avery had already abandoned the Fancy in the Bahamas in 1696. The set for the hold was again in use on February 9th, after which Webb moved over to the spaceship cockpit, where the script identified the deceased pilot as a Skerth. Work there wrapped up on the 10th, with the rest of the day and all of the 11th dedicated to material in the spaceship's medical bay.

Following the weekend, more action in the store and the magazine was filmed on February 14th, together with various inserts. The last day of the main shoot was the 15th, when cameras rolled on the sets for the below-decks area, the magazine and the TARDIS. The time travellers emerging from the hold at the start of the story was also recorded, as were additional pick-up shots. On February 16th, producer Marcus Wilson captured footage of the empty Fancy sets for inclusion in the prequel. This left only Lily Cole's performance as the Siren, which was taped against a blue screen on March 10th and 11th.

Unfortunately, a significant continuity error involving the Boatswain crept into the episode during post-production. As scripted and recorded, he was manacled to the ship's bulkhead after being wounded, where he spitefully revealed the truth about Captain Avery's pirate ways to Toby. The Boatswain later used a sword to break the rusty chains which bound him but, in doing so, he created a reflective surface through which he was snared by the Siren. However, this material was removed in editing, which meant that the character abruptly vanished from the narrative, only to reappear as a patient on the spaceship at the end of the story. The title also changed at this stage, becoming The Curse Of The Black Spot in reference to the first Pirates Of The Caribbean movie.

The eighty-nine-second prequel premiered on April 30th, directly after the transmission of the preceding episode, Day Of The Moon. The Curse Of The Black Spot was broadcast the following Saturday, May 7th. Doctor Who was now scheduled at 6.15pm, a quarter of an hour later than the first two episodes of Season Thirty-Two.

• Doctor Who Magazine Special Edition #29, 14th December 2011, “The Curse Of The Black Spot” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #67, 2016, “Story 215: The Curse Of The Black Spot”, edited by Mark Wright, Hachette Partworks Ltd.