IT all started over lunch at Selfridges in London more than three years ago. Writer Gwyneth Hughes and her drama producer friend Anne Pivcevic were desperate to dream up a project they could work on together.

Biographies had become fashionable with the BBC, and Hughes, exhausted by the long-haul of delivering the original screenplay for five-part crime thriller Five Days, wanted her next project to be a single drama.

"I'd just had a big bill for something, and was a bit panicky but short of ideas," she says. "Then I remembered that I had read Claire Tomalin's biography of Jane Austen a few years previously,
and had come across this amazing thing.

"The woman we all think of as the archetypal spinster wasn't someone who had had no offers of marriage. She'd had an offer from an extremely eligible man who was wealthy and whom she had known all her life. He was a family friend, his sisters were her best friends, and his name was Harris Bigg.

"Had she married him she would have been rich, but she said yes one evening in December 1802, then got up the next morning and said no. Giving back-word was a shameful and appalling thing, so what happened during the intervening night, when she went off to bed, sharing a room with her sister, Cassandra?"

Tomalin had discovered this relatively little-known Austen fact through an account left by Jane's 10-year-old niece, who witnessed the effects of this scandal on the family.

Austen had become a successful writer after years of carrying three completed manuscripts around in her hand luggage but failing to find a publisher. Her book deal, eventually brokered by her brother, earned her a pathetically modest sum, but she and her sister and mother still lived in rural Hampshire in a house owned by her older brother, at the mercy of his fortunes.

Hughes had found the story around which to base a one-hour drama. The BBC loved it, but wanted something longer, which meant finding more of a plot. "Making that one night into 90 minutes needs a real playwright, and I'm just a thriller writer," says Hughes, who does a good line in self-deprecation.

She cast about for another way to tell the story. The key lay in Jane Austen's collected letters, more than a hundred of them published in one volume. Mostly written to Cassandra (who burned many more for her own mysterious reasons), they are witty, gossipy, sparkling and, at times, eye-wateringly bitchy. No retiring, quiet country gel was Miss
Austen, then.

Another half-dozen epistles were written to Fanny Knight, Jane's sweet and naive teenage niece, who was going through a romantic crisis and had evidently appealed to her aunt for advice. Here, signed off with "Infinities of love, J Austen" was the rest of the story.

Effectively, Jane was also her niece's agony aunt, and in telling the tale of how she imparted her wisdom to young Fanny, the narrative of Miss Austen Regrets could also reveal the middle-aged Austen reviewing what might have been had she made different choices. Repeated and forensic reading of the letters – enigmatic gaps in them were as important as the daily detail of walks, mutton chops and excitable retelling of brief encounters – gave Gwyneth Hughes enough fact on which to base a fictionalised account.

Hughes shows us a Jane Austen who is, even as she approaches 40, an accomplished flirt who was comfortable with men, after growing up among eight brothers and a vicar father who took in schoolboy boarders.

"All the men in the story are real and all are mentioned in the letters – some very fully and others not. I took each one and imagined who he was and what kind of relationship they might have had." To Hughes, the least interesting was Tom Lefroy, with whom Austen shared a teenage flirtation, a puppy love previously examined in the rather slight and unsatisfying feature film Being Jane.

How Jane Austen would love all this mulling over the nuances of her life, the poring over every man mentioned in passing. Plagued by insecurity about money in life, how sad that she can't enjoy the royalties generated by the prolific Jane Austen industry, or the
fact that her romances are still regarded as the pinnacle of
serious romcom.

Cracking the big idea was one thing; actually telling a credible story, told in a register that rings true as the voice of the feisty, capricious, clever and complex Miss Austen, was another.

In her conversations with old beau Brook Bridges (played as
the man we should all have married by the gorgeously huggable Hugh Bonneville), we find out that Jane seriously considered him at one time.

Littering the plot with vignettes straight out of Austen – weddings, a picnic, a furious row, carriages disappearing through stair-rods of rain, sisterly affection, and painful truths around love, marriage and money, Hughes always makes it clear that Austen made her romantic decisions because she could not, even for financial security, marry without affection.

The difficult task in the writing was in melding together material quoted from the novels and letters with Hughes's own dialogue. Only the most geeky Austen fan could spot the joins, so seamless is the execution and so comprehensively does she seem to inhabit the writing style of the novelist. It's an near-perfect act of ventriloquism.

Hughes argues that marriage did not elude Jane – and she is shown to have been, at times, almost sick with longing for the security of a marital bed – but in the end she considers her more difficult path well chosen.

"I didn't want her to be seen as the victim of cruel spinsterhood, when the evidence points towards her choosing that direction for good reasons."

That doesn't mean Jane Austen ever stopped thinking about the meaning of love and marriage at a personal level – after all she wrote about them almost every day up to her death in 1817 at the age of 41.

Fanny, trying to separate her aunt's true attitude to love from her frustratingly teasing one-liners on the subject, looks on in bemusement bordering on horror, as Jane flirts outrageously with a handsome young doctor.

But in Austen's letters to Fanny, it's clear that her real counsel was that she must not marry without true feeling – even if, as in Pride and Prejudice, she mischievously shows Lizzie Bennet only beginning to acknowledge her love for Darcy after she sees the size of his mansion.

Taking on part of Austen's life gave Hughes a deeper regard for the writer and her work. "I have to say that I started out on this just thinking it was a cute story. I admired her, but now I love her passionately for her courage. I'm not a brave person at all, and I think she was.

"She role models for me, in terms of 'be who you are, do what you do, and the devil take the rest of them...' She's been criticised (mostly by evil menfolk) for not writing about war and the revolutionary times in which she lived. But for god's sake, she was an entertainer.

"What she wrote about was the sexual politics of her time, and it was serious stuff, as it is today. You can write about human relationships and it can be really important and contemporary, a mirror of the times. In her restricted environment, that's what she did, and that's why the books remain compelling."

The hearts of millions of Jane Austen fans will quiver on Sunday night, to see Hughes's version of the icon brought to life. How many of those viewers will be men is a moot point. She had thousands of male fans in her own day, providing as she did an entertaining and psychologically acute angle on how the minds of young ladies worked.

From empire line frocks to die for, it's back to a life of crime for Gwyneth Hughes, who lives in North Yorkshire and started her TV career as a journalist on YTV's Calendar, before moving into documentaries as a producer and director.

She then wrote for dramas including The Bill and Silent Witness then docudramas like Cherished, the story of Angela Cannings, who was wrongly convicted of killing two of her children.

Production is about to start on her script of the real life story of psychiatrist Jan Falkowski, who was stalked by a woman who then accused him of rape.

A policeman's daughter who feels comfortable on the coppers-terror-jeopardy-murder beat, Hughes has also just finished episode one of another Five Days serial, a follow-up to last year's kidnapping mystery, which was nominated but missed out on a BAFTA this week.

Miss Austen Regrets has already been shown in the US to uniformly rave reviews, even from the fearsome Jane Austen Society. Hughes deflects the plaudits to others – particularly Olivia Williams, who is astounding as Jane. "...if she doesn't win every gong on the planet she will have been robbed."

Ms Hughes has no regrets about her portrayal of JA. "People will find my Jane (and Olivia's) surprising, maybe, but I stand by everything I wrote. It's my account of how she might have been, and I don't think she would have been any gentler or sweeter. She was no shy spinster."

Miss Austen Regrets is on BBC1 at 8pm on Sunday.