There are many pivotal moments in Avengers: Endgame – in fact, the whole movie shifts from one pivotal moment to the next.
But one of the more climactic was thanks to a lovely piece of on-the-spot improvisation from Benedict Cumberbatch, it has transpired.
Director Scott Derrickson, who introduced Cumberbatch's Dr Steven Strange to the MCU, has come with the bombshell.
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Strange, being able to deftly observe time and space, is the one to inform the Avengers during the course of Infinity War that of the 'fourteen million six hundred and five' gamed-out outcomes of the fight between them and Thanos, only one works out.
In a pleasing, but devastating plot dovetail, as it dawns on Robert Downey Jr's Tony Stark that he will have to sacrifice himself for the good of the universe, it's Strange who lets him know that this is the one and only option, holding up a single finger.
Derrickson, after tweeting about the stakes of next week's presidential election - 'No matter what happens, the world is going to feel very different a week from now,' he said – dropped the lovely titbit 'Benedict told me this moment was an improv'.
Derrickson sadly won't be making the next chapter in the Doctor Strange timeline – Doctor Strange in the Multiverse of Madness.
That will fall to Evil Dead icon Sam Raimi, with the movie slated for release on 25 March, 2022.
It's thought that the action will also tie into Disney+ series WandaVision, the 'sitcom' starring Elizabeth Olsen's Wanda Maximoff and Paul Bettany's Vision, and the standalone Loki series, starring Tom Hiddleston as the Asgardian trickster.
WandaVision is set to land in December.
Watch the WandaVision trailer below.