Actress Hannah Waddingham dropped out of a BBC Proms performance hours before the event began to show solidarity with the current US actors' strike.
The Ted Lasso star had been due to host the BBC Fantasy, Myths And Legends Prom at the Royal Albert Hall on Monday.
But that afternoon, Waddingham said she "very sadly" could not go ahead.
"It will be an magical night, but due to my ongoing support for the Sag-Aftra strike I must respectfully step down," she added in a statement posted online.
"I look forward to being back at the Royal Albert Hall PDQ [pretty damn quick]!"
The actress had only been announced as the host on Friday. She was replaced by BBC Radio 3 presenter Katie Derham and Radio 1 film critic Ali Plumb.
The Prom, which featured music from franchises like Harry Potter, Star Wars, The Lord of the Rings and Game of Thrones, was broadcast live on Radio 3 and will be screened on BBC Two on Saturday.
Waddingham, who is best known for her role as Rebecca Welton in Ted Lasso, has been taking on more presenting jobs in recent months.
She was praised for hosting both the Eurovision Song Contest and the Olivier Awards this year. She last appeared at the BBC Proms in 2016.
Waddingham has been vocal in support of both the strike by US actors' union Sag-Aftra and writers' union the Writers Guild of America (WGA), and has been pictured on picket lines in the US.
Members of the WGA went on strike in May and were joined in July by the actors in a dispute over streaming-era pay and the use of artificial intelligence.
Union members have suspended their filming with US studios and are also not allowed to promote their completed work - leaving the forthcoming film festival season with very few stars likely to attend.
However, some actors are allowed to take part in promotional work due to the way their films were financed.
Adam Driver, Mads Mikkelsen and Jessica Chastain are all set to appear at the Venice Film Festival in the next fortnight because their films have obtained Sag-Aftra interim waivers.
The waivers were granted because the films are independent productions and were not produced by major studios.
As a result, Driver will appear on the red carpet to promote Ferrari, which sees him play Italian car racing pioneer Enzo Ferrari.
Chastain, meanwhile, will promote Memory, which features her first film performance since she won an Oscar for The Eyes of Tammy Faye.
Mikkelsen will also head to Venice for the premiere of his film The Promised Land, based on Ida Jessen's 2020 novel The Captain and Ann Barbara.