Oppenheimer stars have abruptly walked out of the British premiere of the keenly anticipated movie, leaving director Christopher Nolan to explain their absence.

Stars including Cillian Murphy, Florence Pugh, Matt Damon, Emily Blunt and Rami Malek were all smiles while walking the black carpet in London on Thursday (local time).

But by the time the movie was due to start, they had disappeared.

Variety reports Nolan was left to tell audiences for two screenings of Oppenheimer that the cast had after learning the SAG-AFTRA strike had been called.

The move was not entirely unexpected; actors including Damon, Blunt and Kenneth Branagh had openly talked about the possibility earlier that night.

The premiere was brought forward by an hour ahead of a Los Angeles press conference by the union, the Screen Actors Guild-American Federation of Television and Radio Artists (SAG-AFTRA).

“Once the strike is officially called, [we’re walking]. That’s why we moved this [red carpet] up, because we know the second it’s called, we’re going home,” Damon said.

“It’s really about working actors. It’s $US26,000 ($38,000) to qualify for health coverage and a lot of people are on the margins and residual payments are getting them across that threshold.

“This isn’t an academic exercise. This is real life and death stuff. Hopefully we get to a resolution quickly. No one wants a work stoppage, but we’ve got to get a fair deal.”

Across town, meanwhile, Australian actor Margot Robbie expressed similar views while promoting Barbie. Robbie told media at the movie’s London premier that she was “absolutely” in support of the actors’ action.

“I’m very much in support of all the unions and I’m a member of SAG so I would absolutely stand by that,” she said.

SAG-AFTRA’s national board of directors voted unanimously on Thursday to approve a strike action for the 160,000 actors comprising the union’s membership.

The move widened the scope of labour unrest in an entertainment industry that already faces numerous headwinds and an ongoing strike by its writers.

The vote came after negotiations between the actors’ union and the major studios – represented in labour dealings by the Alliance of Motion Picture and Television Producers – failed to reach an agreement on a new film and TV contract.

The old collective bargaining agreement expired Wednesday night without a deal in place.

“We are being victimised by a very greedy enterprise,” Fran Drescher, SAG-AFTRA president and former star of TV comedy The Nanny, said on Thursday.

“At some point you have to say, ‘No, we’re not going to take this anymore’.”

While the strike continues, film, TV and streaming productions will stop, and SAG-AFTRA actors will not attend premieres, do interviews for completed work, go to awards shows, film festivals or conventions such as Comic-Con, or promote their projects on social media.

Actors’ picket lines are set to begin in the US on Friday morning, with Blunt indicating to Variety she’ll join them.

The likes of the dual strikes haven’t been seen in Hollywood since 1960 – when Ronald Reagan led the SAG. It shapes up as an extraordinary stand-off that historians and labour experts have attributed to a confluence of cohesion among Hollywood unions, a nationwide rise in labour activism after the COVID-19 pandemic and dramatic technological change.

-with AAP