Ten years of revealing Glastonbury's secrets: How surprises provide the festival's greatest moments

 "Well, you didn't think we were gonna let you down, did you?"

So said Jarvis Cocker as he addressed the enormous crowd at Glastonbury's Park stage in 2011; thousands and thousands of people stood in front of him to see perhaps the worst-kept secret in the festival's history, and one of its greatest live music experiences. The speculation that the then newly reformed Pulp would play the surprise set that day - after Radiohead the previous day, no less - had grown so intense that latecomers reportedly had to be turned away, such was demand.

Beyonce, Coldplay and U2 headlined that year, but like many squashed in the Park Stage audience, squelching in the mud, it was the magic of singing along to Do You Remember The First Time?, Something Changed, and Common People I remember above everything.

Over the years, artists including The Killers, The Libertines, Lady Gaga, Foals and Franz Ferdinand have also popped up "unannounced" at Glastonbury. Last year, an act supposedly called The Churnups, conspicuous by their late-evening Pyramid Stage slot despite being an unknown entity, turned out to be the Foo Fighters.

The festival is famous for its secret sets, surprise guests and big names appearing in unexpected places, so while Dua Lipa, Coldplay and SZA headline this year, it is the TBA slots that may well provide some of the most memorable moments.One person in the know is the founder of @secretglasto, a Twitter account which launched 10 years ago and now has almost 80,000 followers and a small team of six keeping the updates going. They have no official ties to the festival, but over the years have cultivated their sources - from people working on stages to sometimes even acts themselves - so they are "90% confident" about whatever they hint at.

"There's also people that have been good at [revealing] what acts are playing before the line-up comes out," says the Secret Glasto founder (we'll call them SG). "So you can take their word a lot more seriously because they have some way of knowing what's going on - even if you don't know the specifics as to how they get that information, you can see the track record."

When it comes to favourite secret sets, SG names Drenge and Wolf Alice, but says it's "hard to look past The Killers", who turned up in 2017 - 10 years after headlining for the first time, and two years before returning to headline again.