“It’s the culmination of so much, I lived in Dublin for a couple of years and it gave me so much, just walking and feeling part of the tribe here, walking the streets and trying to project and The Olympia is a room where you can hold this gathering and celebration, it’s a gift.” Headlining The Olympia under his own bat obviously means an awful lot to David Keenan. He announced the show a year ago, and may have raised the odd eyebrow in doing so, but he’s proved himself right again with a sell-out, and if the phone calls and emails looking for tickets are anything to go by, he could have filled a few more seats and all.

He appears at about nine to a roar, standing alone, armed with just his acoustic guitar, illuminated on a rug by a few naked bulbs, a silk scarf draped on the microphone stand. He still looks like a young Chaplin, or certainly someone from another age, in his braces, open-necked granddad shirt and slightly over-sized slacks. “Cillian Murphy’s younger, better-looking brother” says Danny McElhinney, a recent convert, sat to my right. He’s not wrong either.

“Speaking the language of my own soul”, a lyric from the opening ‘Big Boys Must Cry’ sums up where he’s coming from, the crowd already singing along. “Thank you all for being here, we made it to The Olympia, we did this together.” Into ‘Full Stop’, snapping at the low E-string, begging his love to appear to him in a waking dream. “Let’s bring back an old friend” introduces ‘Lawrence Of Arcadia’ – “Where are ye” he asks and the crowd responds, “who’s brave enough?” he stares them down as the songs breaks, “Christie!” someone shouts, and Keenan smiles a “good man” as he goes into the next verse. You can’t kid a kidder.

At this point he welcomes out an extended version of his Organics acoustic collective –cello, flute, old pal Junior Brother on both melodica and guitar, the brilliant Gareth Mac Chuinn Mac Réamann on violin and Kíla man Rónán Ó Snodaigh to add colour with his bodhrán – the people who became his friends and let him feel part of a tribe. “Bless The Mad Ones” was in part inspired by touring with Hothouse Flowers and the song goes up a gear as it incorporates ‘Sí Do Mhaimeo Í’, a tune that the Flowers often close their shows with. Ó Snodaigh finds his place in it and it takes off. ‘Postcards From Catalonia’ sees Junior Brother following the melody down on his guitar as Keenan employs his repetition as mantra technique for the “across the city” refrain. 'Two Kids’ is beautifully sung as a duet with Laura Burke, Keenan’s voice hollering and pleading before it goes a cappella to end.

There’s an intermission, necessary for the changeover, which lets the air out of things slightly, as an aerial hoop dancer performs in front of a photographic slide show, and then the curtain drops to reveal the full Unholy Ghosts band in all their glory. Graham Hopkins floor-tom fills the room before a “haon, do, tri” takes us into their theme tune. Harry Hoban is sat behind the keyboard in feathered hat and full Pierrot make up, made slightly Amish by his half beard, Gareth is already dancing about, and there’s the first of the stinging guitar solos. It’s an almighty opening salvo.

The beginning of ‘The Healing’ still sounds like a very distant cousin of Kate Bush’s ‘Army Dreamers’ but quickly goes somewhere else, the crowd joining for the “hold me, I’m only a moment away” line. The guitar and violin double up for the riff in ‘Altar Wine’, Keenan’s voice rising as the song begins to swirl and bubble. “Are you not delirious?” he asks before the acoustic start to ‘Love In A Snug’ which might still be his best song, a perfectly-realised snapshot of a glorious barroom scene, Graham Hopkins’ high backing vocals emulating his hero Levon Helm for that beautiful Van-like chorus that takes us back to the Strawberry Fair, and another sing along as we all tell the rain to go away.

Keenan cajoles us to introduce ourselves to the person next to us, to hold hands, and most of the crowd buy into it, swept along as he tells us that these are our good old days, we’re living them now. The song itself hangs on the scrape and yaw of Gareth’s violin as Hopkins gets a lot of mileage out of an orchestral mallet and a shaker. It’s just Harry and David for a beautiful ‘Tin Pan Alley’, the vocal exploring every corner of the room, emphasising “I.DO.ROAM” and wringing everything out of “songs of o-O-OLD.”

Hopkins takes a brief solo to call in the e-bow guitar and sequencer led ‘Origin Of The World’ and then “teacher, friend, brother” Gavin Glass appears to commandeer the keyboard for ‘Evidence Of Living’, Keenan beating his chest as the crowd repeat his “within them, within us!” declaration, the violin and the collective “ohs” of the backing vocals taking the song to its end before Keenan Scissor-kicks it to touch, although it comes back up again, allowing him to thank us all for being part of this journey before he walks off as the band still play. In a lovely moment, he brings on the little boy who adorns the albums cover; he releases his balloon and tells us we are the living in this town. You may try not to smile, but it can’t be helped.

Someone roars, “Come on the town!” as Keenan returns to the stage alone. He plays “The Friary’, he ignores calls for the ancient history of ‘El Paso’ but does go back to “a song I don’t play very often” ‘A Corner Boy’s Lament’ where he feels “safe among the hawkers and gawkers, telling stories scribbled down on decks of cards”. ‘Seamus/James Dean’ is greeted like a returning child, the crowd, ecstatic, hardly let the singer get a word in, and then the band are back for a song that may or may not be called ‘Badlands’. It’s a new one on me but it sounds like some sort of raggle-taggle run at ‘Gloria’, which is more than all right.

“It was an epic adventure to get here, this thing gives me a sense of belonging in myself” is Keenan’s summation before he thanks all the “teachers” involved “This is the end of the beginning, not the beginning of the end”. It finishes; as it has to, with ‘Subliminal Dublinia’, and all who have taken the stage this evening sing along, arm in arm. There are cheers and screams and two rounds fired from a confetti cannon, but what’s important is the notion projected on the back curtain “Occupy the city with original ideas” It is, as he says himself, a start. A cynic might scoff, but it is at least something, a thought, an idea, a fine notion, and something will always be better than nothing.

‘Smile’, originally written by Charlie Chaplin – which is, I believe, where we came in – plays over the PA as Keenan, slightly teary eyed, takes his final applause. The night is a triumph, the album A Beginner’s Guide To Bravery may be less than a week old but it is already the first great record of the year, the young man has transmogrified himself into an artist through sheer force of will, realising his own vision and bringing more people to it every day. Who knows where this will go?