The A-list cast of filmmaker Christopher Nolan's new movie "Oppenheimer" left the film's London screening midway in solidarity with the strike called by a Hollywood's actors union.

On Thursday, the Screen Actors Guild-American Federation of Radio and Television Artists (SAG-AFTRA) voted to join screenwriters in the first joint strike after failing to reach a consensus for a new contract with the studios and streaming services, represented by the Alliance of Motion Picture and Television Producers (AMPTP).

The London premiere of "Oppenheimer", Nolan's sprawling epic about J Robert Oppenheimer, the theoretical physicist remembered as one of the fathers of the atom bomb, saw lead stars Cillian Murphy, Florence Pugh, Matt Damon, Emily Blunt and Ramy Malek grace the red carpet.

But they left before the screening of the movie in preparation for the imminent strike, the filmmaker announced later.

"You’ve seen them here earlier on the red carpet. Unfortunately, they’re off to write their picket signs for what we believe to be an imminent strike by Sag, joining one of my guilds, the Writers Guild, in the struggle for fair wages for working members of the unions, and we support them," Nolan said at the stage.

The premiere was also moved up an hour so that the cast could walk the red carpet before the SAG board's announcement.

At the carpet, Damon told American news outlet Variety that once the strike is called, the cast will be walking off in "solidarity".

"We talked about it. Look, if it’s called now, everyone’s going to walk obviously in solidarity... That’s why we moved this (red carpet) up because we know the second it’s called, we’re going home," the actor said.

"We gave the strike authorisation. We voted 98 per cent to 2 per cent to do that because we know our leadership has our best interest at heart," he added.

His co-star Blunt said, "Obviously we stand with all of the actors and at whatever point it’s called, we’re going to be going home and standing together through it because I want everyone to get a fair deal.” The strike by Hollywood actors is the first strike since 1980. It is also the first instance when two major Hollywood unions have been on strike at the same time since 1960.

Members of the Writers Guild of America (WGA) have been on strike since early May, demanding better wages, higher minimum pay, more writers per show, and shorter exclusive contracts among other things.

"Oppenheimer" is set to be released in theatres worldwide on July 21.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.