Camille O'Sullivan portrays a male rapist in <i>The Rape of Lucrece</i>.

Camille O'Sullivan portrays a male rapist in The Rape of Lucrece.

CAMILLE O'Sullivan is sounding a little breathless down the line from her Dublin home. But this is not some coquettish affectation. It's just that she's been in a hurry.

''I've rushed home on my bike, thinking, 'I hope I get in before he rings,''' she says in a singsong Cork accent that brings to mind Mrs Doyle, the daffy housekeeper from Father Ted. She apologises again for being late (she isn't) and talking too much (far from it: she's an interviewer's dream).

It's all a far cry from the famously sexy intensity of O'Sullivan's performances singing the songs of Tom Waits, Nick Cave, Jacques Brel, David Bowie and others and in which she might miaow, cry, growl, writhe on stage or even sit on members of the audience, as the mood takes her.

''I probably wish I didn't move on stage and that I was a good, pure performer but I'm the opposite,'' O'Sullivan says. ''There's this other side that comes out and says, 'I think I'm going to crawl for a little while now.'''

O'Sullivan is well known in the industry for being as down-to-earth off the stage as she is flamboyant on it. She was born in London, but at the age of three moved to Ireland's south-east with her mother, Marie, a French-born artist, and father, Denis, a motor-racing driver and champion yachtsman. It was, she says, a ''quite bohemian'' upbringing and the family brought an unaccustomed level of glamour to the small Cork town of Passage West.

''We weren't really accepted in the village to the extent that the Catholic Church wouldn't let my mother enter the grounds,'' she says. ''The local kids thought I was Chinese sometimes because I used to squint at them, pretending that they couldn't see me.''

As a consequence of not quite fitting in, O'Sullivan spent hours absorbed by her parents' eclectic record collection. ''I spent a lot of time listening to Brel and Bowie and stuff and doing performances with my sister. It was quite a creative little household,'' she says.

As well as selling out her quirky cabaret shows at festivals from Edinburgh to Glastonbury, she has co-starred with Bob Hoskins and Judi Dench in Mrs Henderson Presents (2005) and toured with Jools Holland.

Most recently, in another fresh departure, she has starred in a one-woman production of Shakespeare's rarely heard narrative poem The Rape of Lucrece, which features original music co-written with Feargal Murray.

The tragic work tells the story of Tarquin, the son of the king of Rome, who rapes a courtier's virtuous daughter. In response to the violation, Lucrece kills herself.

O'Sullivan plays all the parts, including sexual aggressor and victim, taking advantage of her unique ability to conjure radically different personas on stage. (''Less like a performance, more like an inhabitation or haunting,'' one critic wrote after seeing Lucrece in Edinburgh).

''To every person there is a female and a male side,'' O'Sullivan says. ''The director had come to my show in Edinburgh and she had spotted that I did that thing of singing like a male or female. You don't have to do too many changes to the look of a person, it's just how they think or how they deliver it.

''It's a real pleasure to be on stage and be able to perform this one story and have people come on that journey and believe that you are those four different people.''

Attempting to inhabit the mind of a male rapist must be a unique challenge. ''I do manage to separate who I am as Camille to bring the evil of something so horrible over to the audience,'' she says. ''It does make me think of people I have met in my life and think that they are definitely an aggressor.

''What is amazing with Shakespeare is that he could understand a woman that way. People think of rape as a physical act but he understands that the mind and body are one and once one has been damaged, it is very hard to separate.''

O'Sullivan admits the prospect of performing Shakespeare - especially in collaboration with the Royal Shakespeare Company - was intimidating. Just navigating the rhythm and meter ''as an Irish person'' was challenge enough.

''But they were very kind and said 'just find your own way to express it','' she says. ''At first I hadn't a clue what half the things meant … but they said 'don't let the poetry throw you, there are real people in here and a story' … you must always come to the essence of the story in the end.

''And what was really nice is that we were doing a poem that was kind of unknown,'' she says. ''We weren't doing, 'To be or not to be…' so at least I'm not going to make a complete eejit of myself.''

The Rape of Lucrece is at Southbank Theatre, the Sumner, January 31-February 10.