The path to Slane winds lazily up a hill, rambles under dark-green bowers and smells of fresh damp earth, with the sound and glisten of a river just perceptible, fresh and splashing gently over stones. We walk, and we walk, and then finally the trees open up around us, and in a clearing the road curves around a castle, gleaming-white and round-turreted; and just then - before we come out into the wide green valley, hills and evergreens cradling the Slane faithful all around us, the stage awaiting us at its bottom – before we see all this, we hear music, floating gossamer toward us through the trees.

The gentle wind-carried melodies are courtesy of Relish, the ideal accompaniment to all this unbelievable sun and endless blue sky, who supply proof positive that there is no such thing as playing a festival too early in the day. Hmmm, except that due to traditional traffic-related festival traumas, we’ve missed quite a bit. Happily, we arrive just in time to bask in the wistfully sweet entreaty of ‘It’s You I’m Thinking Of’ - Ken Papenfus’ skylark-soul voice as effortlessly lovely as the breeze that carries it - and to gospel-groove along to the gentle love-in of ‘Rainbow Zephyr’. Even this early on, we’re grinning and hugging ourselves, and everything is very much alright with the world.

Right, that’s enough uncomplicated joy for the time being, thank you very much. The sun may have got its hat on, but as far as JJ72 are concerned, it can fuck right off. Not since their beloved Manics has there been a band who chest-thumpingly bragged, promised, threatened to give us so much, to be the best band in the world, ever. So it’s perplexing when a trio with such a profound and fundamental belief in the grand gesture play Slane Castle – perhaps the perfect festival location to backdrop their cathedral-scaling heights and mucky-hearted depths - and bring so little that’s in any way special to the party.

On the bright side, so to speak, their unholy trinity brings a bit of welcome, if slightly amusing, goth gloom-and-doom to this breathtaking summer afternoon, Mark Greaney in long-sleeved, head-to-toe, fuck-off-sun black, Hilary Woods once again achieving coolest-bassist-ever critical mass (which does not go unappreciated, as sundry gaggles of lovesick boys spend between-song lulls wistfully chanting her name).

And there are some moments of heart-pounding brilliance: the moody petulance of ‘Snow’ apexes in a teeth-bared, bring-’em-on primal scream of feral rage; ‘October Swimmer’ is a perfect, pouting pop single seething with dark malevolent glamour; and the us-against-the-world outcast-anthem of ‘Oxygen’ manages to simultaneously bristle with defiance and wrench us closer like the best love song in the world.

But the troughs in between, littered with adequate but nondescript Smashing Pumpkins castoffs, raise the alarming question of whether they mightn’t have a fourth great song in them – an impression unaided by Greaney’s uncommunicative-cum-snarling onstage demeanour. “Thank you thank you thank you, blah blah blah,” he spits bitterly, and that’s as congenial – and as verbose – as it gets.

This could be nerves, or it could be unforgivable arrogance on this immeasurably significant day: whichever, even the requisite end-of-gig guitar smash is executed with the joyless sullenness of a boy recently requested to tidy his room. This doesn’t, however, stop two dazzled fans from scooping up the splintered pieces, clutching them happily to their chests like priceless artefacts from some strange, violent, and probably very dark, faraway planet.

They’ll be wanting to grab something else in about a minute. Heads up, Destiny’s Child: we don’t think you’re ready for this jelly, because we have witnessed the storming of Slane Castle by some real uber-women, complete with fiery First-Baptist-Church-of-Harlem full-body soul-voices, whiplash musicianship and delightfully normal-shaped female bodies (several of them, with charming down-home unpretension, clothed in U2 T-shirts).

This sexed-up all-girl revue (well, except the drummer) is, of course, led relentlessly from the front by the feral, deliciously husky-voiced space-queen funk wonder that is Kelis. This is girl soul-rock, silky-soft and loved-up but ferocious: Stevie Wonder’s visionary psychedelic-soul jaunts raunched up with rock-funk pyrotechnics Lenny Kravitz spent a whole career trying to ignite, delivered with sumptuous, not to say sex-dripping, confidence and hip-grinding-body-popping sensuality by a lion-maned vision of Parliament-style divahood.

The surprise best of the set is the previously annoying ‘Caught Out There’; what was a man-hating Jerry Springerism of complaint soul as a radio single turns out, live, to be absolutely, positively, completely man-loving instead. “What is this / I see / You don’t come home to me!”, Kelis wails, face contorted, a world of c’mon-baby lover’s pain in her voice, her whole body racked with the ache of it, sinking to the floor in a quasi-pornographic paroxysm of Prince-circa-‘Darling Nikki’ superdesire.

But it’s cool, she’s got her girls: circling her gently like sympathetic sistas one minute, snapping back into formation the next, singing luscious harmonies that would surely coax God down out of his heaven, never mind a straying love-rat back into bed.

‘Shiver,’ indeed. It makes perfect sense for Coldplay to share a stage with the U2 of 2001: the former’s purity of intent, charming innocence and beautiful world-view, and the latter’s band’s recent reoccupation of the spiritual higher plane, could not thrum in more perfect sympathy. There’s the revivalist emotional rescue of ‘Everything’s Not Lost;’ the clear-eyed vision, untainted by notions of cool, that allows Coldplay to gleefully report that indeed, we live in a beautiful world, yeah we do yeah we do. And there’s the fact that they are completely without artifice, pretensions or traditional rock aspirations of grandeur, and yet are not bland or mawkish, but heartracingly, lump-in-throat-inducingly, gobsmackingly good.

‘Yellow’ may well be the only singalonga festival anthem that can bring a valley to its feet without its emotional resonance getting lost in the clamour, without our faith in every word Chris Martin is singing wavering for a second. “Look how they shine for you,” he urges us, so full of joy that we have to look, and it’s only five in the afternoon. The new tunes are just as ravishing, still intoxicatingly dusky and steeped in yearning, but possessed of a thrilling undercurrent, a tide-pull of brand-new urgency that points to more complex emotional navigation ahead, not to mention several more up-with-people killer choruses.

“I don’t wanna get too Cilla Black or anything,” confides Chris, whose pure-hearted candour, if anything, would give him a much higher matchmaking success rate, “but there’s a girl called Janita and a guy called Scott here today, who wrote to us to say, can you please ask us to get married. Kinda like Jim’ll Fix It. So, eh, everyone out here today, says for you to get married. This is for them,” he finishes, summoning the breathtaking northern lights of ‘Trouble,’ its subtle colours and shooting-star incandescence undimmed even in the afternoon sky. A match, we think, made in as close to heaven as you’re likely to get. Positively sublime.

Which can only mean that next up, is the ridiculous. Ba-twannng! goes a bass guitar, and this is how we know the Red Hot Chili Peppers have arrived, in a short-trousered stampede of proto-rap-rock calisthenics, groin-busting 160-degree squat-splits, and of course more slap-bass ‘fun’ than a barrel of teenage funk-enthusiast monkeys.

They seem to be made entirely of sinews, biceps, tendons and muscles, every bass-drum hit underscored with a body-slam, every Peppery surface shaved-smooth, So-Cal brown and more amply tattooed than a battalion of drunken sailors. As such, they are a teenage boy-dream of funk-rock, fundamentally male but oddly sexless, a spotty-geek Wayne’s World ideal of what it is to be a (just about) grown man, to have a quirky, not to say toilet, sense of humour and to be rock stars. Dude. In the audience, right down front, with almost divine-intervention levels of irony, bobbles a bright-pink and gleaming inflatable plastic willie. Huh-huh-huh. Like, settle down, Beavis.

Surprisingly for such a strapped, fat-free, limb-flailing, six-pack-flashing torso-rama of a band, they aren’t - musically speaking - very tight at all: the bass and drums frequently don’t connect; the newer, mellower ‘Californication’-era numbers drag, and even skintight, knuckle-punchin’ early singles like ‘Give It Away,’ despite some Huge Rock Shapes thrown with old-pro expertise by Anthony Kiedis, fall inexplicably flat.

So it’s all about the spectacle, which, given the day that’s in it, is fine. “This next one is an Irish participation programme, if you will,” Kiedis announces, panting a little. “For the entirety of this next musical composition we wantcha to take off your shirts and swing ’em around over your heads like helicopters. Arright?” And just like that, in an insane Guinness Book of World Records-calibre moment of mass disrobing, twenty thousand shirts are whipped off, held aloft and whirled merrily in the waning light like beach-holiday windmills. Irish men being Irish men however, everyone who removes his top still seems to be wearing about seven more layers. Just as well, really.

So the sun has just about set behind the hill, and as we wait, the regular house music blends imperceptibly into tunes that are less trendy-funky, less about the stilted route of fashion and more about the river of soul, tunes full of heart and spirit and simplicity… tunes about the sort of things, as it were, that you can’t leave behind.

‘The Boys Are Back In Town’ – in tribute to the lads’ last Slane appearance two decades ago - segues into the Motown spiritual-pop of ‘Your Love Keeps Lifting Me (Higher and Higher)’, which segues into the vaudeville rock of ‘Sergeant Pepper’s Lonely Hearts Club Band’… and as two bright-red escaping balloons, floating away off into the dimming sky, are fleetingly captured on the DiamondVisions, we get to our feet, hearts swelling, and turn toward the stage.