Cillian Murphy joined his "Oppenheimer" co-stars in leaving the film's London premiere on Thursday night, July 13, as the Screen Actors Guild - American Federation of Television and Radio Artists (SAG-AFTRA) prepared to strike.

SAG-AFTRA’s National Board declared a strike, effective July 14 at 12:01 am Pacific time, and instructed all members to cease rendering all services and performing all work covered by TV/Theatrical Contracts.

With the strike imminent on Thursday, the London premiere of "Oppenheimer" was brought forward an hour. The film's stars, including Co Cork native Cillian Murphy, walked the red carpet at the Odeon Luxe in Leicester Square.

When asked about the impending strike, Murphy told Deadline on the red carpet: “I just stand by my colleagues, that really is all I have to say on that at this point.”

Cillian Murphy on how he physically transformed into #Oppenheimer. Plus, the star lends his support to striking workers...

— Deadline Hollywood (@DEADLINE) July 13, 2023

Fellow "Oppenheimer" star Kenneth Branagh told the PA news agency: “Everybody is working very hard to make sure it doesn’t happen, if it happens I stand in solidarity with our SAG members.

“We know it is a critical time at this point in the industry and the issues need to be addressed, difficult conversations, I know everybody is trying to get a fair deal, that is what’s required so we’ll support that.”

Co-star Emily Blunt told Deadline: "I think right now we are just sort of — I hope everyone makes a fair deal and we're here to just celebrate this movie.

"And if they call it [a strike], we’ll be leaving together as cast in unity with everyone."

When asked if they'll be "upping sticks," Blunt said: "We are gonna have to. We are gonna have to. We will see what happens.

"But right now, it’s a joy to be together.”

Emily Blunt on the current Hollywood labor strikes: “I hope everyone makes a fair deal...”#Oppenheimer

— Deadline Hollywood (@DEADLINE) July 13, 2023

Later, speaking on stage ahead of the screening of the film, director Christopher Nolan said: “I have to acknowledge the work of our incredible cast, led by Cillian Murphy.

“The list is enormous — Robert Downey Jr, Matt Damon, Emily Blunt, Florence Pugh, Kenneth Branagh, Rami Malek and so many more.

"We have to acknowledge, you’ve seen them here earlier on the red carpet.

“Unfortunately, they are 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 their union.

"We support them."

Christopher Nolan says the cast of #Oppenheimer left the premiere to ‘go and write their pickets’ and join the strike

— Deadline Hollywood (@DEADLINE) July 13, 2023

As part of the strike, the guild's first against the film and television industry since 1980, some 160,000 union members have been instructed to withhold a number of services, including promotion and publicity services, likely impacting further "Oppenheimer" promotion before it arrives in the theaters on July 21.

Members of the union must not cross picket lines, SAG-AFTRA said.

According to the Los Angeles Times, SAG-AFTRA’s national board of directors voted unanimously to approve the strike after negotiations between the actors’ union and the major studios failed to reach an agreement on a new film and TV contract.

The SAG-AFTRA strike marks the first time in 63 years that both actors and writers have been on strike at the same time.

In a statement about the strike, the Alliance of Motion Picture and Television Producers (AMPTP) said its proposals included a "groundbreaking AI proposal" that would protect the likenesses of SAG-AFTRA members. 

However, SAG-AFTRA lead negotiator Duncan Crabtree-Ireland said the proposal would result in background performers receiving just one day's pay in exchange for their likeness being used for the rest of eternity. 

"This ‘groundbreaking’ AI proposal that they gave us yesterday, they proposed that our background performers should be able to be scanned, get one day’s pay, and their companies should own that scan, their image, their likeness and should be able to use it for the rest of eternity on any project they want, with no consent and no compensation," Crabtree-Ireland said at a press conference. "So if you think that’s a groundbreaking proposal, I suggest you think again." 

Similar concerns about AI have been raised by the Writers Guild of America, who have been striking since May. 

The WGA has called for the regulation of AI use, including a ban on AI writing or re-writing "library material". The WGA is also calling for a ban on the use of AI to generate source material for writers and a ban on the training of AI tools based on material written by guild writers. 

The AMPTP has rejected the guild's proposals and has instead suggested yearly meetings "to discuss advancements in technology."