When reporting on projects that have not started filming, it's always best to wait for the official press release if you need confirmation on casting. While some trust IMDb, it's too easy for bad actors to edit the cast lists randomly; there are also last-minute circumstances when an actor needs to exit a project due to unforeseen conflicts, and the production has to scramble to recast. However, Sam Mendes' Beatles Quadrilogy of movies seems to have had most of its cast confirmed, not by the production, but by the people who were in the other productions they're going to give up to star in the four interconnected biopics.
We first reported on this in early December 2024, when Barry Keoghan (Saltburn) was confirmed to play Ringo Starr. Considering Starr himself revealed the casting, it seems safe enough, even though the project refused to confirm anything; as multiple outlets pointed out, the deal had yet to be signed, necessitating keeping officially mum.
However, since then, two more castings have been confirmed... by the writers and directors of the projects they'll be leaving behind. Paul Mescal (All of Us Strangers) was first when his Gladiator II director, Ridley Scott, was asked about Gladiator III. Scott replied Mendes had already filled Mescal's dance card to play Paul McCartney.
Source: tellyvisions.org/Ani Bundel