"The Curse of the Black Spot" was conceived as a romp, a more light-hearted episode of Doctor Who (in which there is no evil monster and no one dies) to contrast with the darker themes at the other end of Season 6. It is also notable for two stellar guest appearances: Lily Cole as the siren, and Hugh Bonneville's Captain John Avery providing a relatively rare moment of crossover between Doctor Who and Downton Abbey.

Here are a few things to keep an eye out for, the next time you watch:

(The episode is available on iTunes and Amazon.)

The original title of the story was "Siren," but it was changed to echo the title of the Pirates of the Caribbean movie "Curse of the Black Pearl." The idea of a black spot on the palm that is a harbinger of death is a familiar pirate curse from Robert Louis Stevenson's classic novel Treasure Island.

The real Henry Avery was no soft-hearted seaman. A slave-trader turned pirate, he operated in the Atlantic and Indian oceans in the mid-1690s, and was so notorious that he gained the nicknames "The Arch Pirate" and "The King of Pirates" despite a mere two year career of buccaneering. His ship, the fancy, was part of a squadron of pirates who attacked a treasure convoy in the Indian sea, eventually securing a booty worth £600,000 (around $700million in today's money), making him the richest pirate in the world. A cruel man who led a crew with a reputation for torture and sexual assault, Avery disappeared with his loot in 1696, never to be heard from again.

This isn't the first Doctor Who story to namecheck Henry Avery. His name also came up in the First Doctor adventure "The Smugglers," set after his death. That story deals with a search for Avery's treasure, and where he is mentioned, it is his fearsome reputation that casts the longest shadow, with the Doctor and his companions being told by a Churchwarden that, "His spirit rides... in the dark souls of those who follow in his wake."

Steve Thompson was unaware that Henry Avery had ever been namechecked in Doctor Who before. He found Avery's name by looking through a book about pirates that belonged to his son, and liking the idea of Avery's sudden disappearance.

There are a few items of British slang in the script that are worthy of a mention. Avery calls Amy a "doxy" when sending her down to the galley to cook for the crew. In this context the term—never a compliment—means a woman of easy virtue or prostitute, although it was also used to refer to a mistress. Its origin is obscure, but may come from the old Dutch docke, meaning doll.

Toby Avery threatens a crew member with a cutlass, yelling "one more step and I’ll use this, you blackguard." That last term is a well celebrated item of 17th century slang (also spelled "blaggard"), thought to derive from the lower orders of servants in a fine house. The scullions and lower menials would wear black livery, black shoes and stockings or had hands stained with soot from cleaning fireplaces and chimneys. So a blackguard is on the lowest rung of the household, and to call someone a blackguard (based more on their contemptible behavior than economic status) is to cast them down among the ash-rakers.

https://www.youtube.com/watch?v=IvEdtn179Ro

The Doctor says, delightedly, "We've managed to bagsy a ship where there's a demon popping in!," using the term bagsy, a mispronunciation of the idiom "bags I..." which secures the speaker something they want, whether it's to go first, to take the front seat in a car or to opt out of an unpleasant task. To bagsy something has the same meaning the same as call dibs.

The Doctor remarks to Rory that there are worse ways to die "than having your face snogged off by a dodgy mermaid," using the 20th century British slang verb snog, meaning to kiss passionately.

This isn't Bonneville's first visit to the Whoniverse. He previously appeared in the Seventh Doctor audio drama "The Angel of Scutari," playing Sir Sidney Herbert and Tzar Nicholas I of Russia.

Having built a sickbay in which beds were suspended from the ceiling using strings, the production crew had to ask all the cast members not to move, in case they began to swing and sway in the background. In the end, the beds were so reactive that everyone in shot had to be asked to breathe lightly.

https://www.youtube.com/watch?v=au-mID090Ec&t=2s

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