Mariza, Royal Festival Hall, London

Let's pretend, once again, that we are in Lisboa, in a small taverna," Mariza suggests, looking out at a Royal Festival Hall kept intentionally sepulchral tonight. She is the biggest global star that fado, the darkest and most soulful European music, has had, singing at Olympic Games ceremonies and single-handedly reviving its fortunes. But Mariza is also a purist; open to the international rhythms absorbed on her last album, Terra, but rooted in the traditional fado played at her father's taverna where she sang from the age of five.

She presents herself as exotic yet unmistakably Portuguese, her body's slim top half growing out of a wide black ruffled skirt; a hybrid of pop star and princess. Mariza's music, too, has a professional, modern veneer. Moments of "Morada Aberta" sound like a blowsy Hollywood ballad, and "Barco Negro" climaxes in a small epic of strobing white light and movement. But at the heart of it all is a voice schooled in fado's depths. "Barco Negro"'s real drama comes from Mariza, standing straight-backed in the shadows as if in a witness box, hand warding off despair, and humming with controlled emotion. The hard black-and-white lighting that the strobing creates suggests the art deco set of an old Hollywood musical, where Mariza would fit. At moments tonight, she reminds me of both Liza Minnelli and, in her grand gestures, Malian divas such as Oumou Sangare. Fado began in Portugal's African colonies, after all.

Mariza's band sometimes veer towards jazz. But no one cuts loose on this stage, where the wild abandon of American soul has no place. Instead, Mariza offers a sort of vocal perfection. On "Fado Primavera" she enacts clutched despair and restrained passion, matching her buttoned-up funereal clothes. Even when she flings herself into high, roaring notes, they stay crisply targeted. Her face mimics crying in fado's highest-strung, lachrymose moments, but a real tear is never close.

The effort such careful art takes is shown when Mariza mentions she was shaking as she started this first European show of 2010. The reason she cares so much is shown when she switches off the mics, after more than two hours, and trusts her voice to carry here as it did in the tavernas where she, and fado, began. On her second attempt, that voice reaches into the rafters, at last raw, powerful and right.