Her head still shaven, emphasising the boyish looks, Sinéad O'Connor slipped on stage in hooded top and jeans like a ruffian invited to join the church choir. This was half an hour before the star of the show was strictly due to be there. It took a minute or so for some in the large, boisterous audience to realise she was putting in an early shift with her band, as a backing singer to fellow-Dubliner and startlingly good support artist Damien Dempsey.

When the band returned, O'Connor was centre-stage, minus the top but otherwise unchanged. The bars had been closed at her request, and those hovering at the back were sufficiently restless to treat her opening efforts as mere competition for their conversation.

Soon, however, the irritating chatter was silenced by the amazing thing that is the O'Connor voice. Over the years, one of the strongest emotions stirred in people by O'Connor has been a desire to shake her or worse; Frank Sinatra wanted to "kick her ass" after she threatened to cancel American concerts if The Star Spangled Banner had to be played first.

At 35, she is a mother and, on the face of it, much calmer. Her private life still seems intermittently turbulent and not very private; her public utterances continue to raise the odd eyebrow. But once on stage, barefoot with a crucifix around her neck, she has an unfailing ability to overcome whatever demons trouble her and sing her heart out for an adoring following. O'Connor has long featured Irish folk music in her work and songs from a superb new album of Irish material, Sean-Nos Nua, dominated her concert.

Edgy and self-conscious as she began with Peggy Gordon, a fairly straightforward love ballad which she typically treats as a declaration of lesbian love, she grew more assured as she sensed audience approval. My Lagan Love, lifted by her stunning range and timing, was exquisite.

Once the ancient stuff was out of the way, it was onwards to what she called, without irony, the "old stuff", namely the pop songs most in the crowd had come for.

The huge hit, Nothing Compares 2 U, came early in this section; pleasing but strangely subdued, it was not the highlight. Backed by an eight-piece band, with Caroline Dale outstanding on cello, O'Connor had more to offer. There was I am Stretched on Your Grave for "all the dead people", John I Love You for "children and the crazy".

During a lengthy encore, she grabbed a guitar for the first time and strummed a few harmless chords to accompany The Last Day of Our Acquaintance, even then leaving hundreds of admirers clamouring in vain for more.

Colin Randall reviews Sinead O'Connor at the Shepherd's Bush Empire