Jessie J is back in town for her third iTunes festival in as many years. And as a pioneering pop princess still lagging behind fellow Brit School year of 2006ers Adele and Leona Lewis, she arrives with the bravado of a healthy underdog. Strutting and grinding around the stage in her sparkliest undercrackers like the glamourpuss star of a show called Over-Sexualising Essex, she declares London “my favourite place to party”, and pulls out all the tricks – flames, steam, glitter cannons and an oversized stage complete with mini ego ramp. It’s like being privy to an arena tour rehearsal; at one point an unpractised effect leaves Jessie awkwardly filling time while her crew race around popping a stageful of unwanted balloons.

Jessie J’s problem is that, as an earnest attempt to become Dagenham’s own Tina Turner, she resorts to endless hackneyed tactics from the well-thumbed arena R&B rulebook. Her earlier songs have grown huge, glossy rock riffs that make the likes of Price Tag sound ironically expensive, and she only stops belting out confessionals like It’s My Party (“you’re stuck in the playground and I’m a grown woman now”) to expound soppy fortune-cookie life lessons. “Whatever you carry with you every day, let it go,” she says over wistful arpeggios. It’s part powerhouse pop show, part Jerry Springer’s final thought.

Despite a touching story about weeping her way through recording her forthcoming third album’s breakup centrepiece Your Loss I’m Found, a stool-and-dry-ice ballad section sees the show slip deep into the X Factor quagmire. A shame because elsewhere, when David Guetta’s whoomps drop into LaserLight, Tinie Tempah emerges for a crisp verse on Sweet Talker, and Jessie speed-raps over the gabba techno bits of the frankly berserk Ain’t Been Done, she merges various pop persona – streetwise señorita, motivational sister figure and handbag-flinging party girl – into a style that feels all her own. If only it all sounded less about the money, money, money …