White Riot, the documentary about the UK "Rock Against Racism" movement of the late-'70s, is out October 16. The centerpiece of the film is the famous "carnival" thrown in London's Victoria Park on April 18, 1978 that was at the end of a day-long march from Trafalgar Square which featured over 100,000 protesters. The Clash, Steel Pulse, Tom Robinson Band, X-Ray Spex, Sham 69's Jimmy Pursey and Patrik Fitzgerald all performed.

In this new clip from the film you can watch Pursey join The Clash onstage for the song this documentary gets its name from. It's an electrifying performance in front of a massive crowd for a great cause — Pursey performed after initially backing out when death threats were made against him. ("No one can tell me what to do! I'm here because I support Rock Against Racism.") There's also some present day interview footage with Clash drummer Topper Headon. Watch that below.