Green Day's Billie Joe Armstrong walked into a London bar last night and sang Basket Case with an astonished covers band: watch fan-filmed footage

Green Day frontman Billie Joe Armstrong shocked Saturday night drinkers in a north London rock bar last night (May 13) by jumping onstage to sing Basket Case with a disbelieving covers band.

Clearly a surprise to all involved, Armstrong's spontaneous guest spot with covers band Borderline Toxic at Slim Jim’s Liquor Store on Upper Street in Angel, north London was documented on social media: the band posted their own footage of the performance of the Dookie-era classic on Instagram, with the caption: 'The moment your band gets joined on stage by your childhood idol to sing their own song with you… in your favourite dive bar!! 🥹 Billie Joe Armstrong… @greenday !! THANK YOU, YOU LEGEND! 🔥 This was the first band to get me into rock when I was 11 years old and I’m honestly just so made up 😅🥹 brb crying/screaming/spewing'

Green Day's most recent London gig took place in front of 75,000 fans at the London Stadium last June, as part of their Hella Mega Tour.

Watch the footage of Armstrong's impromptu pub performance below:

Green Day also posted footage online, with the caption, 'When you walk into a pub and the cover band starts playing your song'.

The Californian punk superstars currently have five rather larger shows on their schedule, including two headline appearances at the emo/punk nostalgia fest When We Were Young, which will take place in Las Vegas on October 21 and 22. Other bands set to perform at the weekender include fellow headliners Blink-182, 30 Seconds To Mars, The Offspring, Good Charlotte, Thrice and All Time Low.