[Possible spoilers ahead if you have not yet seen Avengers: Endgame.] During Endgame, Iron Man and Captain America travel back in time to the 1970s to the original S.H.I.E.L.D. headquarters and the military base where Steve Rogers first trained before being selected to receive the super-soldier serum. While there, Captain America observes Peggy Carter talking with other agents.
It is in that moment that we may have either been given a small Easter egg or possibly or possibly confirmation that a 2018 Marvel Cinematic Universe rumor about Phase 4 was true. ComicBookMovie.com reported that Peggy talked about an unseen agent called “Braddock” who “hasn’t checked in.” This could be a reference to Brian Braddock, otherwise known to Marvel comic book fans as Captain Britain.
Flashback to that 2018 Captain Britain rumor…
Seemingly out of nowhere, rumors circulated around many pop culture and fan sites that Marvel Studios was planning a Captain Britain and the Black Knight film directed by Guy Ritchie. At the time it seemed like a legitimate rumor because Marvel may have been trying to fill the void left by Guardians of the Galaxy Vol. 3 with the firing of James Gunn early that summer. It also made sense that the studio would be looking for their next big hero, with many of the original Avengers actor’s contracts ending after what was only know as the Avengers 4 (Avengers: Endgame, as we know now) at the time.
Fuel was added to the flames of these rumors when news of Henry Cavill’s exit from DC’s Superman movie franchise was also announced. Fans immediately starting lobbying for Cavill to don the uniform of Captain Britain. Admittedly, casting Cavill as Captain Britain would make sense for a multitude of reasons. First, it would re-team director Guy Ritchie with the actor as they previously worked together on 2015’s The Man from U.N.C.L.E. In addition, Cavill has the physique and is British, despite his American accent in most of his film roles.
Only time and Kevin Feige will be able to confirm any of this speculation, but here is hoping that we soon see Captain Britain and possibly Excalibur in the MCU soon.