Public Image ltd, 02 Academy, Birmingham

The sneering "'ello-'ello-'ello!" that began the song "Public Image" and the band Public Image Ltd in 1978 reintroduces both as, for the first time in 17 years, John Lydon fronts the band with which he followed the Sex Pistols. Then his trousers nearly fall down. "All that butter," he moans, not missing a beat, "and I've still lost weight... "

The one-time Johnny Rotten advertising butter isn't incongruous, because he remains irreducibly honest, even as he contradicts or lets himself down. Few performers are so thin-skinned, both woundable and wounding. PiL was when he started digging at the scars celebrity and his deprived, diseased childhood had inflicted. He's at his most imposing tonight when the set-list is weighted towards PiL's first two albums, Public Image and Metal Box. The latter effectively started post-punk, and on "Poptones" especially, still feels discomfortingly modern. "Drive to the forest in a Japanese car", Lydon sings with opaque romance, as if an old existential art film is playing in his head. A pretty guitar line loops unsteadily behind him, the tune collapsing several times, then picking itself up. "Shame on you," he pretends to scold at its end. "That is a song about a brutal rape. And you're applauding!"

The most unsettling moments of the song, and his 1979 response to his mother's slow death from cancer, "Death Disco", are when he pretends to weep, mouth kabuki-sad, but the real thing perhaps possessing him. A second later he's emoting as if finally tackling the Richard III that his Rotten persona (hunched by spinal meningitis in his case) grew from. This is rare emotional drama, drawn from music and memories he can't fake. His vocal extremism, from a pure echoing howl down to soft contemplation, is equally great.

PiL's decline gets thrown in too, with the Americanised rock of the aptly named "Disappointed". A gig by them with this line-up in their final year, 1992, would have been ignored, and as a Lydon who expectorates between every song – though "not at other people", he lectures his fellow ageing punks – admits he's "run out of steam", so does the gig. But maybe exhaustion is an energy, because he rallies for a raw, angry "Religion". Public Image Ltd gave Lydon his freedom to be honest 31 years ago. It did so again in tonight's best moments.