It is three years since the Scottish folk singer Karine Polwart burst on to the scene as a songwriter after spells with Malinky and the Battlefield Band.

Her debut album, Faultlines, was voted Best Folk Album of that year, and The Sun's Comin' Over the Hill, taken from the album, was voted Best Original Song. The album's title reveals much of Karine's approach to her craft. She says it refers to the moral ambivalence she sees in much of society - the "uncertainty, anxiety and loss", as she describes it. When you realise that she was once a philosophy teacher you begin to see that she uses her words with care.

But in case you get carried away with the idea that here is a singer whose songs are impenetrable or introverted, you should have been at a full Carling Academy in Oxford last Friday to experience the warmth and openness she creates with her audience.

With the first-rate backing on guitar from brother Steven and multi-instrumentalist Inge Thomson, she opened with Only One Way, an anti-war song written as a tribute to the Oxford campaigner and activist George Monbiot. It combines the sharp, pithy lyrics that run through her songs with a measure of defiance that all anti-war songs commands. The Oxfordshire connection didn't end there as Better Things, written after going on a march against Trident, condemns the nuclear convoys that begin their journeys from Harwell. Given the song, I would have preferred a strident vocal. But that's not her style.

Her popularity owes more to the poignancy and imagery of such songs as Rivers Run, written after the birth of her first child, and Firethief, specially composed on the theme of HIV/Aids for the new version of the Radio Ballads. Both are on her new album, This Earthly Spell, one of two albums recorded in just 12 months - and at the same time as having a baby! A productive year indeed.

The singalong I'm Gonna Do It All was particularly enjoyed by a contingent - teachers or parents? - from Lark Rise school in Oxford, who have adopted the song for a link-up with a school in Uganda. Karine was excited at the thought that her fame had spread so far.

The finale just had to be the very moving The Sun's Comin' Over the Hill, and with an encore of the exquisite Follow the Heron, the night proved a great showcase for her talents.