In the closing moments of Avengers: Endgame, Steve Rogers travelled back in time to return the Infinity Stones and Mjolnir to their rightful place in the MCU's timeline.
At some point on his journey, Captain America decided to remain in the past to get his happy ending with Peggy Carter. His reappearance in the present day suggested he'd lived his life at the same time his past self had been in ice and then fighting alongside The Avengers.
However, the rules established in Loki suggest that Steve's actions created a branching timeline. That's likely to have major ramifications for the Multiverse in Avengers: Doomsday, with Doctor Doom reportedly out to make Cap pay for the Incursion that destroyed his world.
It's previously been reported that Avengers: Doomsday reshoots will begin in April, but it appears cameras are already rolling in London. No actors were spotted on set, but crew members wearing Avengers: Doomsday jackets were spotted filming scenes set in World War II London.
We can't really even begin to speculate about who they are or what will feature in this sequence, though Steve and Peggy Carter seem a safe bet. Of course, this may be one of the alternate realities we visit while exploring the Multiverse and could just be an establishing shot.
Still, we should also point out that this could be for a completely different movie or TV show that just so happened to have a few crew members who previously worked on Avengers: Doomsday on set, wearing their jackets.
UPDATE: This may have been for Narnia: The Magician's Nephew, which is also filming in the UK capital. There's also evidence to suggest the Nicolas Cage-led World War II movie, Operation Fortitude, was being shot over the weekend.
The photos and footage below are from yesterday, so if this is for the next Avengers movie, fingers crossed we'll get our first look at the cast on set in the coming days.
Check out these possible Avengers: Doomsday set photos in the Instagram gallery below.
Avengers: Doomsday officially stars Chris Hemsworth, Anthony Mackie, Winston Duke, Tom Hiddleston, Sebastian Stan, Letitia Wright, Paul Rudd, and Robert Downey Jr. Wyatt Russell, Simu Liu, Tenoch Huerta Mejia, Florence Pugh, Danny Ramirez, David Harbour, Hannah John-Kamen, and Lewis Pullman all make their Avengers franchise debuts in the movie.
The Fantastic Four: First Steps leads Pedro Pascal, Vanessa Kirby, Ebon Moss-Bachrach, and Joseph Quinn join them, as do X-Men franchise stars Kelsey Grammer, Patrick Stewart, Ian McKellen, Alan Cumming, Rebecca Romijn, James Marsden, with Deadpool & Wolverine star Channing Tatum.
Chris Evans is also officially confirmed to reprise his role as Steve Rogers, as is India Rose Hemsworth as Love. The Hollywood trades have reported that Hayley Atwell and Ryan Reynolds will appear as Peggy Carter and Deadpool, respectively.
The Russo Brothers direct Avengers: Doomsday from a screenplay by Stephen McFeely, with whom they previously collaborated on the Avengers and Captain America franchises. Loki and Doctor Strange in the Multiverse of Madness's Michael Waldron is also working on the script.
Avengers: Doomsday is set to be released on December 18, with Avengers: Secret Wars scheduled to arrive on December 17, 2027.