Two years ago, Grohl's band - the rock behemoth that is Foo Fighters - were meant to headline Glasto, capping a journey that began with their first single, the still-exhilarating This Is a Call, in 1995. But then Grohl broke his leg and they had to cancel.
It's been a long road here...
1. Nirvana: the greatest band Glasto never had
Before the Foos, Dave was, of course, the drummer in Nirvana - the grunge act whose hooks were better than most pop bands, and in the early 90s were the biggest band in the world, their t-shirts everywhere from Dudley to Delhi.
But Nirvana never played Glasto - maybe they were too loud for the cows? Fortunately they became festival legends at Reading instead, in 1992, when Kurt Cobain came on-stage in a wheelchair and surgical gown to mock rumours that he was ill. Dave was just 23 at the time and unrecognisable. By which we mean he didn't have a beard.
2. The Foos' Glasto debut is almost rained off
The Foos have been at Glasto before - once, in 1998, when they were third on the bill below James and Primal Scream. But even if you were there you might not have noticed them. It was raining so hard, it looked like the Foos were playing on the other side of a waterfall.
But the torrential rain and threat of trench foot didn't stop the show from turning into a heaving sing-and-mosh-along, especially when the band launched into hits like Monkey Wrench and This Is a Call. Grohl's showmanship helped too, quipping at one point: "This is for the tall guy in the red shirt, just 'cause you're the only one I can see."
Dave recently told Radio 1's Annie Mac about his memories of that night: "We we were in our infancy then. We were halfway down the bill. It was pouring down with rain and I think there was some sort of Euro cup final thing happening, so about 90 per cent of the audience disappeared once we hit the stage."
Clearly not his fondest memory.
3. Grohl of the Stone Age
Dave has been back at Glasto since 1998. In 2002, he was the temporary drummer for Queens of the Stone Age, playing some of the sleaziest, gnarliest rock music ever to grace the Glasto fields. Dave played topless while wearing black fingerless gloves, all his sweaty tattoos visible. He could have quite easily walked straight off-stage and into one of Glastonbury's naughtier after-hours dance tents!
4. A jump too far
I think I just broke my legDave Grohl
As mentioned above, the Foos were meant to headline Glasto in 2015, but just days before they played a warm-up show in Sweden and everything went wrong. Two songs in, Grohl went to jump on a ramp but missed and fell into the security area. "I think I just broke my leg," he told the crowd as he lay on the ground. "I'm going to go to hospital. I'm going to fix my leg. And then I'm going to come back."
It sounded like the words of a hysteric, a rock God overcome with pain. But Dave was true to his word. Unbelievably, just an hour later, he returned to finish the show. One gig-goer told 成人快手 News what it was like: "He reappeared after an hour to continue the concert, sitting in a chair with his leg bandaged. It was surreal to see him perform on stage with a medic holding his leg. The crowd was just amazed that he was carrying on. He was just phenomenal."
Dave clearly never wants to disappoint, but doctors insisted he couldn't do Glastonbury. Damn you, doctors! However, he soon resumed the tour, seated in a special guitar-pronged throne.
I think I just broke my legDave Grohl
5. There in spirit
Florence and the Machine triumphantly stepped in to headline Glasto in the Foos' place, but that didn't mean Grohl et al were absent: Florence sang a glorious, trumpet-filled version of Times Like These as a tribute to the leg-smashed band. "We would like to dedicate this next song to the legend and all-round incredible human being Dave Grohl," Florence said. "We hope through the Glastonbury ley lines this gets to you and you feel better. We're sending you so much love."
Grohl was watching Florence that night. "I saw footage of them playing Times Like These and I got really emotional and thought, 'What a beautiful gesture'," he told Annie Mac. "I can't wait to play that song. I've been thinking about this for two years. Playing a song like Times Like These in front of that audience for the first time, standing up on two legs, is huge.
"It's a big deal, personally. It's part of my recovery in a weird way."
6. And so, it's 2017 and...
Not a moment too soon! A Foos Glastonbury headline performance at last. Here's Run from their new album - the 13th song the band played, just before launching into This Is a Call. They'd opened with Times Like These, and you can see closing song Everlong below. Was it a goodbye? Nah, as Dave says: "We never really say goodbye, we just say this..."