Who: Mumford & Sons.

Where and when: John Peel stage, 7.30pm, Friday.

Dress code: For the band, it's a strict khaki-and-white theme; trousers, vests and grandad shirts, with only double bassist Ted Dwayne in a denim shirt. For the audience, straw hats and beards in evidence.

What happened: This time last year, Mumford & Sons were playing to 300 people on the Greenpeace stage. Now, they're so big that the John Peel stage can barely hold them – the crowd stretches way beyond the tent's parameters and every single song is received with rapture. If Mumford & Sons weren't already huge, and the music biz fully expects them to "do a Coldplay", this performance would make them so – it's a stunning show of strength. Multitasking (in Marcus Mumford they've got that rare creature, the singing drummer), crowd-pleasing (the entire audience seems to know the words to White Blank Page) and possessing the ability to raise the roof using not much more than a mandolin, at this rate it won't be long before they're headlining the Pyramid stage – or failing that, the moon.

Who's watching: A crowd whose size would impress by any standard, even more so considering that the competition was Dizzee and Florence.

High point: Penultimate song The Cave, which inspired a singalong so fervent that resistance was simply futile.

Low point: Their inevitable success will inspire some insufferable bands.

In a tweet: Mumford & Sons is open for business. Big business.