Martha Wainwright, Bloomsbury Theatre, London <!-- none onestar twostar threestar fourstar fivestar -->

This was an evening that lent fresh meaning to the term "intimate" - and, for that matter, "spontaneous". It made you feel like you'd been invited back to the Wainwright place (or the McGarrigle place) for Christmas to knock back a few egg-nogs as the family gathered around the fireside with banjos, mandolins and accordions. "Drink up!" Martha advised during one of rather too many interludes to tune her guitar. "It'll sound better like that."

An air of ramshackle spontaneity hung over the evening, with Wainwright a cheerfully chaotic ringmaster, missing cues, banging into microphones, snagging guitar leads, forgetting who was on next and messing up songs: "I'm so sorry," she apologised at one stage, "I really thought we were having a moment."

The truth was, this was an entire evening of moments, all of them magical, from the opening bars of "Factory" to a full-blown chanson finale of Barbara's "Dis, quand reviendras-tu?".

In the intervening two hours Wainwright, with a little help from her friends and family, showcased the extraordinary range of a voice that spans all the emotions from languid regret to defiance and rage. First came the relatives - mother and aunt Kate and Anna McGarrigle, and cousin Lily Lanken - followed by friends Beth Orton, Thea Gilmore and Chris Stills.

Wainwright's self-lacerating songs paint her as a sort of Bridget Jones figure but her closest musical reference is Lucinda Williams who mines a similar seam of painful honesty at romantic disappointment. "You're all the same with your balls and chains," Martha puns in "Ball & Chain". But there's a soft centre, too: "I have no children, I have no husband, I have no reason to live - Oh, give me one," she sings in "Far Away", a song that distils the melancholia of a woman hearing the tick of her biological clock.

It's reassuring, at least for her fans (if not the singer herself), to report that a generous batch of new songs, written as she approached her recent 30th birthday, suggest that Martha's self-esteem issues remain refreshingly unresolved. Plenty more material for her next album.

The McGarrigles were given the stage to sing Wainwright's favourite song by her mother, "Talk to Me of Mendocino", before daughter returned, alone, to sing a spellbinding version of her finest song, "Bloody Mother Fucking Asshole". Her father, along with brother Rufus (the butt of several barbs) will doubtless be glad that he gave this particular family evening a miss.