Vicky Pryce knows what it is to be judged by the media, but if I was expecting icy reserve from her, I don't find it.

The woman standing before me in the kitchen of her elegant London townhouse is smiling and apparently relaxed, if a little distracted by messages on her mobile phone.

A year ago, Pryce was a prisoner at HMP East Sutton Park, sleeping in a dorm, and responsible for cleaning the dining room after breakfast; today, in a few hours' time, she is speaking at a conference on economics. A respected expert, she has returned as an unpaid adviser to the Department of Business, Innovation and Skills and is in demand for speaking events. The piles of papers covering the kitchen table have a semi-permanent look and as we chat while she makes tea, she comes over as a woman who has got her life back. Superficially, at least.

But what is going on behind that composed exterior? That question lingered throughout her trial last March for taking the penalty points clocked up by her former husband, the one-time Liberal Democrat Cabinet minister Chris Huhne.

The events are well known and relate back to 2003, when Pryce agreed to take Huhne's points when his car was registered speeding on the M11 (Huhne, then an MEP, had been returning from Brussels).

The offence might never have come to light, had it not been for Pryce's reaction to her husband's admission, seven years later, that he intended to leave her after 26 years of marriage for his PR adviser. The break-up left her "practically suicidal", Pryce later told the court.

Pryce subsequently tipped off two Sunday newspapers that Huhne asked someone to take his points, in a bid to "nail" him. A police investigation was launched, the estranged couple were questioned and in February 2012, they were charged with perverting the course of justice.

Then Pryce chose to lodge the unusual defence of marital coercion and the scene was set for painful revelations about the couple's marriage, including that the economist had had one abortion (under pressure from Huhne, she claimed) and had resisted having another.

In the end, it proved all to have been in vain, when the jury convicted them both. The judge said Pryce had been motivated to reveal Huhne's offence by "an implacable desire for revenge, and with little consideration of the position of your wider family". He told the pair: "Any element of tragedy is entirely your own fault." They were both sentenced to eight months and Pryce served nine weeks, first in Holloway and then at East Sutton Park open prison, before being released with an electronic tag.

Journalists were fascinated by Pryce, who refused at any point to conform to anyone's stereotype of the scorned woman crazed with anger. She was firmly in control of herself throughout, as encapsulated in the pictures of her going into Southwark Crown Court; she was so well turned out, so preternaturally calm, a smile always seeming to play on her lips. The cameras scanned her face for signs of distress, but she never gave them the satisfaction.

Since her release last May, Pryce, 61, has written a book, Prisonomics, which is part memoir of her time behind bars and part economic evaluation of the justice system and how it handles women. In it, she recalls the efforts she made to maintain composure during her trial. "Looks are important," she writes, "as you cannot afford to look despondent and beaten in front of the photographers and the court artists, who exaggerate any negatives. I had taken very good care every day to appear smart and coordinated and relaxed. Not easy."

Today, too, she is impeccably turned out, slim and stylishly dressed in business attire. Pryce, who was born Vasiliki Courmouzis in Athens and calls herself by the surname of her first husband, has had a stellar career. Having come to the UK as a teenager before securing a scholarship to the London School of Economics, she went on to high-earning senior positions at KPMG, Exxon Europe and RBS as well as being the first female chief economist at the Department of Trade and Industry. She also has five children (two from her first marriage and three from her second). She is a lifelong feminist and is deeply concerned by the way childbearing affects women's earning power ("There's a pay gap the moment you take any time off, so I didn't take any time off.")

Her accent still bears a trace of Greek. When I ask about the delicate gold band on the fourth finger of her left hand - have I missed something? - she laughs: "No no no, I've worn them all my life because my father gave them to me. He died some time ago. I'm not remarried," she assures me with a smile, "not for the moment anyway."

Pryce is clearly a woman of formidable determination, but she also seems oddly breakable, perhaps because of her slight build and the way her signature spectacles accentuate her large eyes. She speaks rapidly, but softly - so softly at times I have to lean in to hear her.

She is animated about the plight of women prisoners, but constantly veers off discussing anything personal. Any talk of Huhne is off limits. Perched on her sofa in what begs to be called the drawing room, filled as it is with period furniture and artworks, she is keen instead to talk about the subject of her book, which she will be discussing at the Aye Write! festival in Glasgow next month with the governor of Barlinnie Prison, Derek McGill.

In the book, she talks a great deal about the impact of press intrusion. It seems a contradiction, then, to have offered up her prison experiences for public consumption: did she not wish to sink beneath the radar? "I knew full well that I couldn't so there was no point in trying to hide," she responds. "Since people wanted to hear what I had to say and since so many women I met can't actually have anyone listen to their issues, I thought I should give something back and make sure the women's voices were heard."

Prisonomics relates her experience from the moment she was taken down (she had prepared her children for being away five months) to her early experiences after release, but, like so much about Pryce, is carefully controlled. She expresses no distress, nor any regret. Most of her observations relate to the way her fellow inmates - "the girls" - are treated. It is rather as if she has looked upon the whole experience as a research exercise - researchers, of course, being somewhat detached from their subjects.

She is not coy about this, admitting that writing the book "put me in control, because I had a task" and that she looked upon it like she has looked on professional assignments in inhospitable places. Prison, she reasoned, could not possibly be worse than the shabby Hotel Bowani she stayed in in Zanzibar in the late 1980s.

The upside of this approach is that she has produced an excellent summary about the failures and idiocies of the criminal justice system's treatment of women. She notes with exasperation how the female prison population rose 85% between 1996 and 2011, when crime was steadily going down; she talks of the huge number of women with mental health problems in prison and the much greater incidence of self-harm among them than among male prisoners.

She is scathing about a system that locks up women for "relatively trivial" offences such as non-payment of TV licences, when they are no danger to society, and how doing so is not only expensive, but also costs families dear as many children of women prisoners go into care. It doesn't happen like this in countries such as the Netherlands, she notes, where women are more often given community sentences, and have lower recidivism rates. She strongly advocates more education and vocational training for women, stressing its benefits in reducing reoffending.

She notes at one point that prison can be the result of "a wrong decision … a momentary misjudgment". One wonders if that is an oblique description of how she sees herself. No, she says firmly, she wasn't describing herself, but the experience of women who get caught up in a criminal activity by being part of a group, for instance. Often these women are victims, she points out, who are under someone's influence. That is not how she sees her own situation? "No, I was very much referring to the cases I had seen."

But does she believe she deserved a custodial sentence?

"I've never really questioned the sentence I was given, I have to admit," she claims. "I completely accepted what happened. I accepted I had made a mistake and the jury and the judge decided in a certain way, and that was fine." Nothing to see here, move along please.

Pryce knew nobody who had served time and mentions how taken by surprise she was by the press photographers banging on the van when she was being transported from court to prison in a black maria. She did not know prisoners should lie flat on the floor to avoid being photographed, she explains. "I would never do that anyway, but I was completely unprepared. So I just stood there, smiled a bit, looked outside." The photographers got their shot. The incident "horrified" the other prisoner travelling with her and the guards, she says, and their reaction was the first reassurance she had that prison was going to be OK.

On arriving, she found she had a cell to herself. Was she afraid? "No," she says emphatically. Why not?

She pauses. "I always thought I was reasonably resilient, but also, I had become so convinced that I was going to go to prison anyway. I knew I had survived very, very tough environments before. But of course I could have been completely wrong."

She says that she did not cry when sentenced, nor at any point subsequently. Really? "I can't remember shedding a tear. It is possible that I might have done, but I don't remember."

But surely she must have been upset at times. "Obviously you worry about what happens on the outside, so that can't leave you particularly calm, but I was determined to survive and in such a way that I came out all in one piece."

She was lucky to be going back to a loving family and comfortable home, she says. Many women don't have that advantage.

Pryce clearly paid close attention to press coverage while inside and quotes the Prime Suspect writer Lynda La Plante writing that she could expect to face cat-calls and abuse. But it was nothing like that, was it? "Absolutely not," she says with a dismissive laugh. She had a sort of celebrity status, as the other prisoners had seen her trial. She was only at Holloway for three days, but when going about in "the movement" - the changeover time when prisoners leave their cells en masse to go to activities - she describes being treated with kindness. "You would hear 'Vicky Pryce, Vicky Pryce' coming down the corridors, and they would hug me. Which was really rather nice. And indeed they looked after me when I arrived."

She was quickly moved to open prison in an old manor house where there were bingo and karaoke nights. "Lovely", is her recurring description of her fellow prisoners. The picture she paints of the mutually supportive, confessional atmosphere confounds stereotypes about aggressive bullying prisoners. She does admit she saw some bullying in prison, but "very, very little". For herself, she made good friends and still sees them. "They are people I really trust now," she notes. "It's extraordinary. We didn't have to help each other, but we did."

The relentlessly positive nature of her memoir, royalties from which go to the charity Working Chance which helps women ex-offenders find work, has prompted some raised eyebrows. The former Tory minister Jonathan Aitken, imprisoned in 1999 for perjury, has taken issue with Pryce for portraying herself as so brave, and above all for failing to express any remorse. Does she think that fair comment? Pryce sighs. "My view has been to look ahead rather than look back. There's no point in going through this because then you just open up all sorts of things and it doesn't help the case I'm making." Whatever she feels about the crime, trial and her behaviour following her marriage break-up, she is not sharing.

She is uncomfortable discussing her character, but does use the word resilient.

"Resilient, yes," she says, "although you have to work at being resilient." She hesitates and at last, the veil shifts slightly. "You could easily … we all face periods when we are vulnerable and there are particular things you never get over." She is no longer in declaratory mode, but reflective. "The question is, what do you do with it all? One wouldn't be resilient if one didn't have support. I think family and friends are the most important things there are."

One senses that being seen to emerge triumphantly from her ordeal has been very important to her. She tells me with pleasure about a positive write-up she got after a reception she attended at Clarence House last month ("Vicky Pryce back in the fold").

Pryce is not in a nine-to-five job ("yet") and says she does not know if she wants one. Has she had any problems finding work? She hesitates, but then answers: "When people come out of prison there's a huge prejudice against them and I would be astonished if there isn't some prejudice about me too doing particular types of things. Fortunately there seem to be lots of other things that people are keen that I should do." She is planning another book, this one making the economic case for gender quotas (no, she agrees, she is not one to shy away from controversy). Might she go into politics? She doesn't rule it out.

Through force of will, Pryce has turned the most crushing, humiliating experience of her life into a platform from which to create an authoritative new voice.

Does she now feel at peace? "I have children and grandchildren, four grandchildren, and one of the good things has been that I've been able to look after them a bit more. You realise how the family needs you which is rather nice in many ways."

And then she comes to it.

"I suppose I am reasonably at peace, but frankly if one could wave a magic wand and say 'do you want your old life back?' I probably would use it. I'd say 'yes, please'." She hesitates, lost in thought about this hinted-at regret. "But it won't happen, and that, of course, just never goes away. That never goes away. You can be at peace but still be aware that things are so different than they were." n

Vicky Pryce talks about her book Prisonomics at the Mitchell Library, Glasgow, at 7.30pm on April 7. Visit ayewrite.com for tickets. Prisonomics is published by Biteback, priced £16.99.