An artist who deals in musical passion and drama needs to make a suitably startling entrance, as Mariza is clearly aware. A solitary double bass was playing when she began the first of her emotional, declamatory ballads from behind the drapes, and there was just enough light to see her appear on stage. Tall and elegant, Mariza was acting out what must have been a pained love story as she made her stately procession towards the audience. There she was joined by the other two members of her impressive acoustic trio, playing guitar and the lute-like Portuguese guitar. She paused and suddenly switched to a breathy whisper. Here was a singer not frightened of showing emotion or taking chances.

Mariza, in her 20s, is something of a phenomenon. She is a young exponent of fado, the music that has played much the same role in Portugal as the tango in Argentina or flamenco in Spain. Now she is likely to become a celebrity to British world-music audiences as well. While her appearance at Womad in the summer was impressive, she was far better suited to the Purcell Room. These were songs that needed an intimate and hushed setting.

Even so, there was variety in her repertoire of exquisite and passionate ballads. Mariza had just enough English to explain that "not all fado is melancholic" before embarking on a cheerful song about Lisbon, or one about wine. But she was at her best with her songs of tragedy, such as the story of a girl watching her lover set off to sea while village women tell her he'll never come back. This chilling little tale was performed largely to percussive beating on the sides of the double bass and guitar.

Mixed in with all this were stories of her childhood (she was born in Mozambique and brought up in the Lisbon neighbourhood of Mouraria, a traditional home for fado) and a reminder of the music she sang as a teenager: an unexpected burst of Pink Floyd. Then there were stories of the raunchy history of early fado singers (an excuse to lift her long, black-and-white skirt to show striped stockings), and a demonstration of the way fado was performed in Mouraria. Finally Mariza and her trio walked out into the audience - performing with no amplification, yet still sounding, and looking, as dramatic as ever.