Flashback to November 2015, and with filming now wrapped in Malta, production on TOOM (or Time Out Of Mind, the film's top-secret shooting title) has moved to the mercifully less melty 007 Soundstage at Pinewood. Despite the geographical shift, Pinewood is still doubling for Spain, with the bulk of the legendary soundstage reserved for the concrete corridors and clinical chambers of Abstergo Industries' Madrid facility. Instead, the action has skipped forward five centuries to present day, where Aguilar's descendant, Callum Lynch (Fassbender again) is using the Animus to relive his ancestor's memories. Lynch and Aguilar may look identical, but the blood relatives start the film in very different places.

"Aguilar is somebody who belongs to the Creed; he belongs to a philosophy of thinking, and he is willing to sacrifice himself for the greater good of this philosophy," Fassbender says of the 15th Century Assassin. "And then you have somebody like Cal, who's a total lone wolf. From an early age his family was taken away from him, so he looks after himself first. This idea of sacrifice and becoming part of something is a journey for him.” Despite the obvious challenge of playing two characters in a single film, the magnitude of the task didn't dawn on Fassbender till he was on the set of his next movie. "It only really occurred to me – it sounds bizarre – but I just did Alien [Covenant]. I'm playing two robots in that. I thought, 'Shit! I've just done two films where I'm playing two characters, people will think I'm narcissistic and greedy!'"

For Callum, the first step on his journey is somewhat unorthodox: an 11th hour reprieve from death row. Tucked against the back wall at Pinewood, past sterile sleeping quarters that make Abstergo look part-prison, part-psychiatric institution, lies the execution chamber of the Huntsville Department of Criminal Justice, where convicted murderer Callum Lynch is due to die from lethal injection; a fittingly tragic final destination for a man whose mother was murdered by his own father (Brendan Gleeson) while still a child. Cal is "saved" by Abstergo scientist Sophia Rikkin (Marion Cotillard), who switches the lethal cocktail for a toxin that merely feigns death, so he can help her with her studies – to identify, isolate and eradicate the genetic markers that inspire violence in humans. "I think it's a very noble thing to dedicate your life to end violence," Cotillard says over the phone from Paris after a brief pause for childcare duties. "I really loved her dedication and her faith, because she's not in this Assassins and Templars war at all." Unbeknown to Sophia, Abstergo is a front for the modern-day Templars, who need Aguilar's memories to track down a powerful artefact that could turn the tide of the war.

The war between Assassins and Templars has raged for centuries, but isn't based on claims over land or some ancient feud over stolen chickens. Rather, it’s ideological – the Assassins fighting from the shadows for free will, whatever the cost, while the Templars use religion, societal institutions and now science to instil benign control, believing it the only way to keep people safe. The freedom-fighting Brotherhood may seem the more virtuous in the wake of surveillance culture concerns, but part of the appeal for Kurzel was the absence of clear-cut heroes and villains. “You’ve got these two very different ideologies that, at any time, can be corrupted. They can go extreme. With the Assassins, what's the extreme of free will? It's anarchy. What's the extreme of the Templars? Well, that's control. It was definitely something we wanted to play with – that lovely grey area of, 'Who's the baddie and who's the goodie?'"