Stella Duffy: An empress for our times

Whether writing about Byzantium or south London, the author is always politically engaged, she tells Stephanie Cross

Some nicknames require explanation. Others, such as that of Stella Duffy's latest heroine, speak for themselves. But "Theodora-from- the-Brothel" isn't just any tart-with-a-heart: this Theodora is the Byzantine empress, born in AD500 to the daughter of a hippodrome bear-keeper, who ascended not just to the title of Augusta, but also sainthood.

Her rise was the subject of Duffy's previous novel, Theodora (2010), a book irresistibly subtitled "Actress. Empress. Whore." Duffy's new novel, The Purple Shroud, resumes Theodora's story and isn't – but might be – glossed "The Power Years". And, like its predecessor, it doesn't lack for drama.

"I do believe that power corrupts and absolute power corrupts absolutely," Duffy states when we meet. Yet if her Theodora is a Mrs Machiavelli, determined to wear the purple imperial chlamys until she dies – "Purple makes the perfect burial shroud," Theodora informs her husband, the Emperor Justinian – she is also "the people's Empress", and in her devotion to duty even recalls our own monarch. "She's more Evita if she's anybody," Duffy counters. "Because she's common. And that's why she's so amazing."

Duffy learnt of Theodora while attending a crime fiction festival in Italy. Taken to visit the huge mosaic of the empress at Ravenna, she was captivated by Theodora's story, but realised she had too much material for one book. Material that included the AD532 "Nika" riots which devastate Constantinople early in this novel.

Duffy was editing these scenes at the time of the London riots. "I don't think that people go out doing those things to change the world," she says, when we discuss last summer's triggers. But "there has been more stop and search … Under the kind of cuts the Tories are choosing to bring in, we are getting a bigger difference – and God knows it was bad enough under Labour – between the very rich and the very poor. And again, it's never an excuse, but it is a reason."

Emphatic, witty and vital, Duffy shares much with her heroine (brothel experience aside). "She's an improviser: it's what I did for years … she does things that upset people, because of her politics ... And she has great faith: I do too." Duffy became a Buddhist in 1986, and while her trajectory has not been quite as steep as Theodora's, she speaks with pride of her journey from "council estate in Woolwich to little timber town in New Zealand and very nice three-bedroom house in Loughborough Junction."

Born in 1963, Duffy was the youngest of seven. Her father was a New Zealander and when Duffy was five he moved back with his wife and two youngest children to New Zealand. Duffy had no notion that she would become a novelist: "When you grow up in my kind of family, you don't think you're going to be a writer, cos that's for posh people." Instead, she studied English in Wellington and went on to work as an actress. Duffy returned to England in 1986 and joined an improv company whose members included Jake Arnott and Patrick Marber. Improvising, she says, taught her to write.

Duffy's first novels were crime fiction; "a couple of magical-realisty ones" followed, then the Orange-prize longlisted State of Happiness (2004). "People have tried to call it my cancer novel," Duffy grimaces – the illness, for which she was successfully treated, was diagnosed only after she had started on the book. Nor does the C-word appear anywhere in it, as Duffy points out, her aim being to write about the effects of illness more generally.

Before Theodora, Duffy's last novel was The Room of Lost Things (2008) – "very south London gritty realist" – a book that centred on two male friends. Duffy has claimed that she is taken more seriously when writing about men, an assertion that she stands by. "I often say in this context that when Mike Leigh writes about families, he's considered universal. When a woman writes about families, they're considered domestic." I point out that Theodora earned praise from several male critics. "Rome gets reviewed by men," she responds.

While Duffy is a magpie in her subject matter – her next book is to be set in south London one hundred years ago – she is unlikely to become a chronicler of the Hampstead set. "I don't live in a world where everyone's white. I don't live in a world where everyone's straight. I don't live in a world where everyone's my age … I want to reflect that in my books." Does fiction have a duty to be politically engaged? "YES! Yes. And I reserve the right to write frippery." She laughs.

Duffy's resistance to pigeon-holing extends to her personal life: "No one ever says 'He's a straight; she's a heterosexual,' but I'm constantly being called 'a lesbian' and it's just not the most interesting thing about me," she sighs. Duffy is, however, a vocal crusader for gay marriage. Out since the age of 18, she and her partner, the playwright Shelley Silas, entered into a civil partnership in 2004. "If they bring [equal marriage] in the life of this parliament, we will have been together for 25 years before we could get married," she says, both exasperated and incredulous.

She shows me her wedding ring, its inscription, "Magnificent you", a reference to her cancer – the disease to which Theodora, having swept all before her, ultimately succumbed. "I said to Shelley I wanted to be magnificent with it. I want it to magnify me, not diminish me." Looking back on her illness, Duffy sees it as a watershed. "Not that I wasn't driven, and determined, and an achievement freak before, but … I know that time is limited. And I really want to do everything." As with her imperial heroine, one imagines little standing in her way.

The Purple Shroud, By Stella Duffy

Virago £16.99

'I am your Empress, sir. I stand in the purple beside you, here with your men, your advisers, your generals. I know it has been said that too often I speak where a woman should remain silent. It may be inappropriate, but this crisis does not call for what is appropriate, it calls for what is right.'