He swore he would never play Glastonbury again after headlining with Oasis nearly 10 years ago - but on Friday Liam Gallagher's Beady Eye kicked off events at the festival.
With the words "Get in" and a moment of silence while he surveyed the crowds, the singer launched into "Flick Of The Finger", the first song to be heard on the Other Stage at Worthy Farm this year.
Despite the relatively early hour and the mud underfoot, thanks to a downpour of rain that lasted all night, thousands of people turned out to see the band. Their performance was unbilled but Gallagher had dropped heavy hints about it on his Twitter account.
Although the Mancunian was wearing sunglasses, they were mostly not needed as grey clouds hovered over the Somerset site, with the sun trying to break out.
The biggest cheers came for Oasis hit Rock 'N' Roll Star and, perhaps aptly for the time of day, "What's The Story Morning Glory", which turned into a mass singalong.
Fan Hayley Storey, 30, from Leeds, said: "We only came this way because we wanted a beer - we'd not heard they were playing.
"It's a great way to open the festival. I'm so glad they did Oasis stuff too."
Chris Goode, 35, from Greenwich, south-east London, said: "It was quite a surprise to see them. It was just luck.
"I didn't think Liam would be up this early in the morning. I bet he's not even been to bed yet."
Gallagher had previously complained about the sound system at the festival after Oasis played on the Pyramid stage in 2004.
He apologised to festivalgoers for making their headaches worse if they had one, and told them with his typical swagger as the set came to a close: "You've been amazing. But not as good as us.
"Have a good day, weekend, life."
His partner, Nicole Appleton, was among those watching the performance at the side of the stage.
Gallagher declared: "Glastonbury's back in the good books."
Speaking backstage immediately after the gig, he said of his earlier comments on the festival: "I was probably just having a bad day. I take it back. I just had a bad experience last time."
He said the band, who released new album BE earlier this month, even enjoyed the time slot.
"Absolutely loved it," he said. "I still can't get my head around it. It's mad, innit?"
Band mate Andy Bell said of their early secret set: "It was like a practical joke, and we loved that."
Gem Archer added: "The only time we usually sing before midday is in the shower."
Beady Eye were unable to stay for the rest of the festival, with their tour bus leaving in the afternoon.
Gallagher claimed this was because he had to play the role of "super dad" to sons Gene and Lennon, who were also backstage.
"I've got my kids. I'd probably end up getting wasted and leaving them here," he added.
He said he was tempted to stay and see bands including The Rolling Stones and Mumford & Sons though, asking his bandmates: "Shall we stay forever?"
Gallagher said the festival had got better, crediting the organisers for its success.
"It's Michael Eavis, isn't it, and the family who run it," he said. "They put a lot of work into it."
Celebrities spotted at the festival today included Florence + The Machine singer Florence Welch, who was seen near a backstage bar with writer Caitlin Moran, and Made In Chelsea's Millie Mackintosh, whose boyfriend, Professor Green, was in the Pyramid Stage line-up today.
Professor Green could barely contain his excitement about his performance.
"I was like a kid on Christmas Eve last night. Everyone's here for the same reason - to have a good time.
"If you go up to the stone circle in the night, you see it for what it is. It's like a medieval village.
"This is the first time my gig's on a Friday and it means I can get on stage, get off stage, then get stuck into what Glastonbury's all about."
He said he had enjoyed Haim and Jake Bugg and was looking forward to Portishead and the Arctic Monkeys.
Mackintosh, at her first Glastonbury and accompanied by her parents, looked the part in a floral garland made by a friend and leather hotpants teamed with a khaki top.
She said: "I'm enjoying the hippy vibe. It's the biggest and the best festival.
"I'm not looking forward to the lack of a hairdryer, though."
Rita Ora brought a touch of glamour to Pyramid Stage in a red fringed outfit as the sun blazed over the revellers during the afternoon.
She performed hits "We Run the Night" and "Hot Right Now", telling fans: "We're here to celebrate music today, am I right?
"Thank you so much for having me here.
"Are you feeling a bit hot out there?"
Other stars backstage included opera singer Katherine Jenkins, Bridesmaids actor Chris O'Dowd, his wife Dawn O'Porter and presenter Caroline Flack.
O'Porter said: "I'm so looking forward to seeing the Rolling Stones. I feel privileged to see them in my lifetime. Everybody's going to go totally nuts.
"I'll have my phone in the air so my dad can listen."
The author and reporter wore a psychedelic-print dress for the first day of the festival, and added: "I wanted to go for bright, retro clothing while the weather is nice.
"But if it rains then vanity goes out of the window."