Katy B, Roundhouse, London

(PA)

Fresh from her Mercury Prize nomination in the morning, Katy B bounds on to the stage.

Earlier this year, the 22-year-old from Peckham had a No 2 hit with her debut album On a Mission, taking her distinct dubstep and garage-flavoured pop songs into the mainstream. Despite her continuing meteoric rise, there's something strikingly natural about the star who bounces across the stage tonight, comfortably dressed in black skinny jeans and silver sweater, that set her apart from such attitude-driven popstars as fellow Brit School alumna Jessie J.

Perhaps it has something to do with the fact that Katy, born Kathleen Bryan, started out as a guest singer, first as Baby Katy on DJ NG's album, and later providing the stand-out track on Magnetic Man's album, suggesting that she was never after pop stardom in the first place.

Not that she doesn't cut it onstage. Cute as a button, with a mane of bright red hair, she is keen to strike a level with her fans. "This one's about being in a club and looking at the person next to you and you know nothing about them, but you feel you have so much in common", she says, introducing "Perfect Stranger". A club frequenter since she was 16, it's this experience that she draws from in her observational lyrics.

Performing her songs – her effortless R&B vocals turning dubstep and garage arrangements into pop gems – to a crowd of young revellers could not be more natural. Live, her singing is even more impressive; no amount of pogoing and on-the-spot running affects her singing. Things take off with "Broken Record", her voice soaring effortlessly. Her live band throw everything into the show, too, the two-man brass section of trumpet and saxophone bolstering the two-step jazz and Latin vibes.

In a winning medley of Nineties dance hits, all injected with her dubstep sound, Katy and her band move deftly from Soul II Soul's "Back to Life (However Do You Want Me)" into Crystal Waters' "Gypsy Woman", and Robin S's "Show Me Love", sending the crowd into euphoric enthusiasm. "This one goes out to all the ravers out there, especially if you were around in the Nineties. I kind of was." It's a highlight to match the faster paced club hits that work best tonight, her first Top 10 single "Katy On a Mission" and "Lights On". On this evidence, Katy B's mission is not set to be a fleeting one.