JUMPING from a piano, hurling a stool off stage with frenzied excitement and singing through a megaphone; it was jazz alright, but not quite as you know it.
Jamie Cullum was out to rip up the unwritten rule book of the genre; transforming it effortlessly into something more cool and distinctly rock and roll.
It wasn't forced like some kind of ill-thought out stunt. This was simply a talented musician living in the moment; enjoying every second and sweeping the audience along with the force of a tsunami.
Come the final song we rose as one and stayed there; furiously clapping along to the beat, joining in the vocals and latterly jumping up and down like football fans reacting to a goal.
It was quite a sight to behold in the Big Top - one woman even looked as though she was head banging at one stage such was her passion for the task in hand.
Of course, in true middle class fashion, there were casualties. Rarely has so much prosecco been spilled in such close quarters.
Backed by a brilliant 11-piece band which certainly lived up to Jamie's generous introduction as "among the best in the country", he showcased tracks from his new jazz album which he admits is "the first actual jazz album he's ever made."
For many, premiering material at a festival, let alone the opening gig of such an established one as Cheltenham Jazz, could have been a risk.
But such is Jamie's love of performing here - "I think there's a real danger I might even enjoy this more than you," he joked with the audience - it was only ever going to be a success.
It was a set that was incredibly well judged; one minute stripping it back with a haunting cover of Surfjan Steven's The Seer's Tower and the next upping the tempo with the infectious When I Get Famous from 2013 album, Momentum.
His new material dominated but old favourites reared their head too with Jamie leaping about the stage one minute and producing a spine-tingling cover of Pure Imagination (of Charlie and the Chocolate Factory fame) the next.
There were stages when the band became a little too powerful and even Jamie's strong vocals were struggling to compete. But these were rare moments indeed.
Plus, in truth, they didn't matter. Diminutive Jamie's showmanship proved the decisive factor.
In front of his watching parents he worked the stage endlessly; singing on the piano,leaping from it and dancing around the Big Top with a megaphone in his hand as phones flashed ferociously.
He engaged with the audience like old friends and when one bellowed 'I love you' he paused and whispered: "I love you too - and you know that's genuine. Are you married?," he added, "because I am and my wife will kick your arse." Anyway, he said, let's sing a song about casual sex.
And so he did. Then he sang a little more; a cover of a Randy Newman's Losing You before entering ballad terrority with nods to the likes of Nina Simone.
It's incredible to think that this is a man who used the pain of not finding love at school as lyrics for his song "sit back and watch my scrawny frame," he sings in When I Get Famous. "All the years you've caused me pain."
Sharp-suited Jamie's had the last laugh of course with a model girlfriend, a talent that has made him millions and the everlasting love of his legion of fans.
On this outing, it's not hard to see why.