Within seven minutes of BBC1 picking up live coverage, Chris Rock gets in the first “C’mon motherfuckers”. This shortly after David Gray and Damien Rice have murdered “Que Sera Sera”, Snow Patrol have yelled, “Looking forward to Spinal Tap? We are!” and Geri Halliwell has walked onstage to say, “Isn‘t it great my band are back together?” While the eight concerts around the world constitute an immense, well-intended event, the Wembley show is a thoroughly surreal mish-mash of deafening hard rock, weightless aerobic pop and celebs spouting platitudes.

Nine hours in the gleaming new stadium splutter and frustrate, momentum thwarted by the brevity of the 22 sets. With music for most tastes but satisfaction for none, it’s falling between 22 stools. And then, almost annoyingly, Madonna saves the day. With nobody grasping the nettle and laying claim to voice of a generation status – which was up for grabs – this hugely overpraised woman has a night where everything she does comes off. Accompanied by Gogol Bordello for a “gypsy interpretation” of “La Isla Bonita”, thumping through a pneumatic “Hung Up” and littering “Ray Of Light” with guitar feedback (she’d cased the crowd), she made the communal memory all about her.

It’s a long, patchy day, the lack of tone set by Chris Moyles’ barked nothings. “You’re all on the telly!” Genesis kick off: lesser pros than Phil Collins would have struggled to deal with the sight of 70,000 people getting their bearings while a band plays hits from the worst part of their career. “Turn It On Again” is a crisp rain of chords which Razorlight can’t match, although Johnny Borrell’s much-castigated bravado carries him far in this context. The equally popular and unfashionable Snow Patrol are made for this venue, and “Chasing Cars” (very moving, if you let it be) hits the far penalty spot.

A hint of “atmosphere” arrives with Kasabian, who commendably perform like it’s the biggest gig of their lives. With their Union Jack shirts and Leni Riefenstahl rabble-rousing, Kasabian are visibly trying (which is great), if a little too hard.

After Al Gore via satellite tells us we’ll save the planet, Paolo Nutini sings four songs, which is some kind of bathos. Black Eyed Peas raise the temperature (hits, energy, even a woman on stage), then Duran Duran provide comic relief. Seeing Simon Le Bon huffing and puffing through a Sly Stone cover is funnier than seeing everyone from Boris Becker to Ricky Gervais to Thandie Newton introduce pop groups they’ve barely heard of. “Notorious”, mind, rocks.

Red Hot Chili Peppers roar bloody-mindedly into action (“Dani California”, “By The Way”) like Hendrix never left The Isleys, and the headbanging audience is unanimous. It becomes evident that what’s required is squealing guitars, and loud. Which doesn’t bode well for Bloc Party, who at least have the humour to demand a Mexican Wave, or Corinne Bailey Rae (whose duet with John Legend on “Mercy Mercy Me”, the most considered cover of the day, is impeccable), or Keane, who are and always shall remain the Ikea U2.

Russell Brand promises Satanism and insults Germany, then Metallica turn it up to 11. They are unconscionably loud. “Enter Sandman” could be heard in, and raze, Gdansk. It sets us up nicely for the return of Spinal Tap, who during “Stonehenge” and “Warmer Than Hell” intentionally fail to erect a miniature Stonehenge but succeed in luring dancing dwarf-monks onstage. For “Big Bottom” they’re joined by nine bassists. Sadly, the crowd look at The Tap like they don’t know who they are. Perhaps that’s even funnier.

The Beastie Boys transcend cartoon japery to sizzle through “Sabotage”, Pussycat Dolls wiggle their behinds, then Foo Fighters rev up. “Times Like These” and “Best Of You” prove you can growl with pathos. Dave Grohl’s unit have become Britain’s favourite hard-rock band by stealth: all age groups scream along, and Grohl nervelessly struts the catwalk like the sixth Pussycat Doll. He exhibits great charisma for such a man’s man.

It’s still not enough, despite a dignified speech from Terence Stamp and the symbolic dimming of Wembley’s lights, and when Madonna opens with “Hey You” (Elaine Paige doing “We Are The World”, complete with children’s chorus) the worst is feared. But then she hits the zone. The rest is, possibly, history.

Thanks to Chris Roberts for this review