I'll Be Your Mirror: Portishead, Alexandra Palace, London

(Rex)

Portishead's 1994 debut, Dummy, was so perfect it almost instantly became a cliché, a cul de sac they only escaped with 2008's aptly titled Third. But on the first night of a festival the Bristol band curated and headline, they dig deeper into songs it had seemed would bury them, expanding their sonic terrain of scratched hip-hop, vintage vinyl spookiness and Cold War spy movie cool, Billie Holiday and John le Carré.

It's the day Amy Winehouse reaches her tragic end. But news hasn't reached inside Alexandra Palace, and watching Beth Gibbons, I'm thinking she's one of the best singers in Britain. Hunched over like a crippled penitent, she summons the beautiful, low misery of "Wandering Star", while on "Nylon Smile" she defines the potency of fierce female desperation. She's a resolute victim, a needy yet aloof diva, her voice a torch singer's cracked, reedy weapon. Recognising she wasn't built for fame, Gibbons has wholly avoided interviews, remaining a mystery and probably quite ordinary. All she is to the crowd is this mesmerising singer.

Though powerful visuals play behind them the band are silhouettes on stage, absorbed into and liberated by the music -– the woody beats and treated, slow twang of "The Rip", and pumped-up "Blue Monday"-style electronica of "Sour Times". Adrian Utley's rasping guitar solo and shivering strings signal "Glory Box", a vinyl copy of Dummy spinning on-screen as Portishead reach its crescendo. When this drops out and Gibbons cries back in, it's pure jazz, and so perfect it makes me gasp.

Underground hip-hop icon El-P's Company Flow and Bristol reggae veterans Black Roots are among the rarely seen treasures Portishead have brought in support. Their West Country peer PJ Harvey also takes the stage earlier, looking like a crow in a feather headdress. She's in mourning black, suiting her Mercury-nominated new album Let England Shake's bitter refutation of British wars. Half the set's taken from it. Ex-Bad Seed Aussie Mick Harvey duets on Gallipoli lament, "The Colour of the Earth". But the lyrical intent isn't put across by astringent, driving folk-rock. PJ Harvey moves in what shadows there are as bright sun fills the early evening hall. She's for once a well-received sideshow to Beth Gibbons's main event.