Amy and the Doctor's conversation outside the Tower of London could not be filmed at the genuine location due to the London Olympics, so it was shot on studio in Cardiff and the live action was combined with other footage to create the illusion.
For this episode, the title logo's texture resembled the Shakri cubes featured prominently in the episode. Also, the shade of red in the time vortex appears to be more crimson, rather than orange, with the lightning strikes causing an additional effect of electrical surges spreading out from the tips of the bolts. The vortex also turns purple with the sharpness seriously decreasing when the Title appears.
One major element removed from the script was the appearance of Prime Minister Stephen Carter. Suspicious of the Doctor, Carter would bar him from the United Kingdom, resulting in the Time Lord's absence from a long stretch of the narrative.
Chris Chibnall described this episode as "a lovely big Earth invasion story" but different from the ones done before, as it focused on Amy and Rory's time with the Doctor and the impact of him on their lives.
Kate Stewart mentions having "ravens of death" in the Tower. There are six captive ravens that are cared for and live in the real Tower of London. Legend has it that these ravens are the guardians of the Crown and the Tower, and if the ravens ever go away the kingdom will fall.
There was an extended action sequence in the climax in which Rory took down the two orderlies. The Shakri was not a hologram, and instead was defeated when Amy and Rory attacked him with the syringes retrieved from the orderlies, and the Doctor used his sonic screwdriver on the Shakri's devastating ocular weaponry. However, it was felt that this part of the episode detracted from the focus on Amy and Rory's life together.
Chris Chibnall was also inspired by the story of the MSC Napoli, a 2007 shipwreck along the Devon coast near his home, when people showed up in droves to claim merchandise which had washed up on the shore.
The trivia items below may give away important plot points.
This was the last episode filmed with Karen Gillan and Arthur Darvill. The last scene shot was of their characters entering the TARDIS with the Doctor. When the doors closed behind them, all three actors hugged each other and began to cry.
The episode originally ended with Amy and Rory deciding to take "one more" trip in the TARDIS despite Brian's unease. Steven Moffat suggested that this be changed to have Brian encourage them to go with the Doctor, providing a less sombre and more subtle lead-in to Amy and Rory's final story, The Angels Take Manhattan.