A band booked to play a smaller festival stage found itself headlining and playing to a 30,000-strong crowd after the main act had to cancel.
The duo had just finished playing to 2,000 people on the Europa stage when they were asked to replace Swedish singer Lykke Li on the main stage.
Gemma Cullingford of Sink Ya Teeth said it "felt surreal".
Other main acts on the festival bill included Liam Gallagher, The 1975, The Roots and Skepta.
Cullingford, who formed the band with Maria Uzor in 2015, said: "We met the promoter of the festival, Michael Kascak, after having played our set in a large marquee in the afternoon which had gone down well to an audience of about 2,000 people.
"Michael thanked us for playing and said he'd enjoyed the set.
"Maria and I then went to enjoy the rest of the evening... when all of a sudden Michael found us and asked if we could play in place of Lykke Li as she'd had to cancel due to travel disruptions."
She said with about 40 minutes until the sound check it all "felt surreal".
She added: "I couldn't stop laughing. We were aware that we were pretty unknown there so didn't know if people would stick around to watch, but it became apparent there were people there that had seen us earlier that afternoon that enjoyed it, and we played to a full and appreciative crowd.
"It's still not sunk in for either of us yet."