The Last Night of the Proms is under threat as furious BBC staff prepare to swap Union Flags for union placards.
Workers are set to strike over the Beeb's plans to slash pension payments.
Broadcasting union Bectu is planning the walkout on the final two nights of the Proms in September.
Bectu's Luke Crawley said: "If the BBC doesn't back down it could easily find itself with a blank screen - and no one in the Albert Hall, except a very angry audience."
He added: "It's grossly unfair and a complete betrayal by the BBC to its employees."
The 48-hour strike may also be supported by actors' union Equity and the Musicians' Union - meaning many of the performers could also walk out.
