The American music website Pitchfork is the journal of record for alternative America. It has became this generation’s Rolling Stone, for both good and ill. Long before it was bought by Condé Nast, however, it was famous for a disastrous jazz review in which the site’s founder chose to employ what he appeared to believe was the vernacular of a jazz ‘cat’ of the early 1960s.

All is forgiven, though. Here was the London outpost of the Pitchfork Festival, opening with jazz stars Ezra Collective, the quintet who earlier this autumn won the Mercury Prize for their second album, Where I’m Meant To Be. Ezra Collective are very easy to like. Their music is a fast-acting suffusion of gaiety and joy, utilising the strongest-known ingredients for the rapid delivery of pleasure: Afro-Cuban jazz and salsa, Afrobeat (the west African 1970s style, not to be confused with Afrobeats), accompanied by reggae, soul and hip hop.

This was the gig at which the cork popped out of the champagne bottle

Ezra Collective are rather more upbeat than you might imagine from the tenor of some of their press, which suggests you’re about to get Ken Loach set to music. In fact, they’re so firmly committed to the sunny side of life that drumming band-leader Femi Koleoso at one point gave a long speech in which he explained the difference between happiness and joy, an issue to which he had devoted intense thought without quite reaching a clear conclusion.

I could drag up things that bothered me. There were times it all got a bit Shakatak-y, hitting a jazz-funk groove that didn’t seem to have any intention of going anywhere interesting. They briefly dally with compulsory fun: the audience were commanded to stand up and greet each other after the first song. And putting the three ballads with guest singers one after the other in a single block stalled the momentum of the show.

I could drag these things up, but they wouldn’t counter how I felt at the end of the two hours: overwhelmed by the open-heartedness of the group and mesmerised by the ferocious insistence of their music (the man next to me danced so devotedly that his lack of deodorant became a bit of an issue by the end). This was the moment, the single gig, that every band must hope for: the coronation. It wasn’t just that this was Ezra Collective’s biggest headline show yet. It was the fact that it was coming off the back of the Mercury win and the ever-growing celebration of the new British jazz scene. This was the gig at which the cork popped out of the champagne bottle. You could see it on their faces, too – on that of tenor saxophonist James Mollison especially. When he wasn’t playing, he was often simply standing, arms at his side, beaming into the vast, dark space in front of him.

It’s one of music’s most exciting experiences, to see a band live at this precise moment: when they must feel as if they are holding on to a firework and all they can see are the sparks and the glitter and the bright, blinding light. Both audience and performers seemed keenly aware of what was happening. Certainly, the two fed off each other. The stalls sang horn lines back to Mollison and trumpeter Ife Ogunjobi, while the band simply drove on, harder and higher, demanding the crowd follow them.

And, just when you thought it couldn’t get any more ecstatic, it did, with dozens of members of the youth performance group Kinetika Bloco brought on stage to dance and add a great many more horns, as confetti cannons exploded. The whole evening felt like an antidote to these times, a sudden blossoming of unconstrained exuberance. It might just have been the gig of the year.