In the spotlight: How Camille O'Sullivan sashayed from the drawing board to the cabaret stage

Almost exactly a year ago, at the beginning of the Edinburgh Fringe festival, the award-winning architect turned cab-aret chanteuse Camille O'Sullivan emerged from the wings of a packed, steamy Spiegeltent and sashayed through the crowd in a blood-red cocktail dress, kissing and caressing male and female audience members like a purring cat.

In the provocative world of the Fringe, such behaviour is nothing shocking. But when accompanied by O'Sullivan's version of Nick Cave's "God is in the House" – a twisted ode to small-town mentality – it became rather menacing and unsettling, especially for the visibly trembling man in the front row over whom O'Sullivan draped herself as she whispered the song like a caustic lullaby.

An hour later, in the climactic moments of her show La Fille du Cirque, O'Sullivan was on the verge of emotional collapse. Distraught, dishevelled and in floods of mascara-streaked tears, her spectral version of Jacques Brel's "Marique" – a yearning prayer to a lover lost in battle – proved to be one of the most moving moments of the entire festival.

It was clear that O'Sullivan had turned her performance into a personal catharsis, cabaret as black art. And the flustered man in the front row was still quivering with mesmerised fright. "I actually met that guy after the show," she says, "and he said, 'I'm a scientist and I've never seen anything like that.' I just said, 'Don't worry, it happens all the time.'"

A year on, I meet O'Sullivan at her home – a Victorian house off the South Circular Road in Dublin – where she is preparing for her return to the Fringe with The Dark Angel, a show fusing Weimar cabaret with the songs of Nick Cave, Tom Waits, David Bowie and, increasingly, the likes of Radiohead and Nine Inch Nails. It's hard to believe this is the stage siren, full of tears, fire and ethereal fragility, of last year. "People sometimes think they know me because of the show," she laughs. "Then they meet me and I'm going [in a high, fluting Cork accent] 'Oh hello, how are ya, I'm from Cork...' But when I'm on stage, I become this other creature and do things I'm not really aware of. I honestly look at myself on video and think, that's atrocious, cover yourself up woman."

O'Sullivan's half-French, half-Irish name tells its own story. Her mother, Marie (who introduced Camille to the work of the Belgian singer-songwriter Brel when she was barely out of the cradle), is from Bordeaux and met her Irish father, Dennis – then a Formula 2 racing driver – in a café in Monaco. Camille and her older sister Victoria were born in England, but their father wanted them raised in Ireland and the family moved to a village called Passage West, just outside Cork.

On leaving school, her parents guided her toward architecture and she enrolled at University College Dublin, where she took part in every stage production she could find: "I struggled at university; I liked architecture but I loved performing. At that time, though, I hadn't found my own voice. So I took a year out and went to work in an architects' practice in Berlin."

There, O'Sullivan regularly attended cabaret clubs, and on returning to Ireland, by coincidence she met the Berlin-born Agnes Bernelle, one of the last great cabaret singers, then in her seventies, whose father was a contemporary of Marlene Dietrich and who wrote songs for the Kit Kat Club, enshrined in the movie Cabaret. "Agnes had ended up in Dublin and she gave me the best advice: to do this right, you have to be a better actress than a singer, it's all about the story."

After O'Sullivan qualified in 1996 with first-class honours in her degree, and the highest highest mark in the university in a decade, she worked as an architect for four years, winning an Architectural Association of Ireland award. But she was leading a double life – by day, she designed buildings from Donegal to Dublin; by night, she donned fishnets and feather boas and took to the stage. "I was obsessed with performing," she says. "I used to sit in my office thinking how much I wanted to be singer. I needed to make a decision."

A horrific ordeal helped make her mind up. In 1999, O'Sullivan was involved in a near-fatal car accident that left her hospitalised for more than a year. Her skull was fractured, her pelvis shattered and tendons in her hands were shredded. It was months before she was able, with the assistance of a frame, to walk.

Her recovery was agonisingly slow, leaving her with a metal plate in her hand and steel pins in her legs. It is something she avoids talking about; as a self-sufficient, self-managed woman she hates to receive sympathy. Pushed to discuss the accident, she says quietly, "It was touch and go at one stage. I had to learn to walk and use my hands again. But it was a turning point. I stopped thinking 'What if?' and decided to leave architecture to dedicate myself to cabaret."

She admits that when she came out of hospital in 2000, she was "scared of the world". But with the help of her ex-boyfriend, she performed her first Dublin show on crutches. At a time when cabaret was a faded novelty, this was not, to say the least, the safest career choice. "I did three gigs that year," she says. "Nobody wanted to know, especially in Ireland. But I refuse to do corporate stuff. I wanted to go elsewhere in a show, where people are not passive. Cabaret had been diluted and I wanted to make it relevant again. Then, after Chicago [the stage musical and movie], cabaret suddenly became popular again."

Popular it most certainly is. Following her three-week sell-out show at last year's Fringe, O'Sullivan toured Sydney, Toronto and New York, and last month played at Glastonbury, where she closed her rock-festival debut by tearing into David Bowie's "Moonage Daydream" dressed in only a red corset and wellies.

Having become something of a Fringe icon, O'Sullivan regards her current run at the Queen's Hall as a spiritual homecoming. After that, she's off on her first full UK tour – a far cry from her Edinburgh debut in 2004. That time, she lost "a pile of money", but any disappointment was tempered by the fact that she caught the eye of the actor Ewen Bremner (Trainspotting's Spud). Bremner recommended O'Sullivan to Stephen Frears, who gave her a part opposite Dame Judi Dench and Will Young in his 2005 film Mrs Henderson Presents. The architect who ran away with the cabaret has worked solidly ever since.

Are there any regrets about leaving the day job? "I'm a free bird, I don't want to be hemmed in," she says. "I love over-dressing and becoming someone else. But maybe I can design one more building that I'd be really proud of. I think I've got that in me."

'The Dark Angel' is at Queen's Hall until Wednesday and tours the UK from 31 August. Go to www.camilleosullivan.com for details

Passion wagon: The burning lights of new cabaret

Ute Lemper

German-born pioneer of contemporary cabaret. Began in a local punk band before becoming a leading light of the international cabaret revival. Songs delivered with a Dietrich–like cool. Currently touring Spain, then the US and Poland

Meow Meow

Raucous, edgy, neurotic cabaret- punk comes from this diminutive, classically trained American who counts David Bowie as a fan and mainly sings original, spiky material. Made her Fringe debut last year. Currently playing in New York

The Tiger Lilies

Macabre theatrics come from the UK's only cabaret-burlesque puppet collective. The cult band with the eerie falsetto-voiced frontman have expanded their line-up with a fire-eating dancer for their Fringe debut, "The Seven Deadly Sins"

'La Clique'

A fiery mélange of new cabaret and an erotic adult circus from the Australian team behind The Famous Spiegeltent. Expect surprises; Camille and various other top-end performers were discovered and flourished in "La Clique". Performing at the Spiegel Garden, Edinburgh Fringe