The accusations were heinous, but the blonde, a 26-year-old nurse, vowed to stand by the man she'd been seeing on and off for the past four years.

Studying that picture the next morning, Abi Titmuss worried about how she looked, and about how this would change her life. In The Secret Diaries of Abigail Titmuss she writes, "It's such a weird feeling seeing yourself on the front of a national newspaper . . . the anonymity that we all take for granted, gone with the publication of one headline."

Less than two years later, at 5am on a July morning, Titmuss stepped out into a Hackney street to hail a cab. Anonymity be damned! She was stark naked – bar a pair of Jimmy Choos – and having a blast. How life had changed. She now commanded a small fortune as a glamour model and sometime telly presenter, and earned thousands more making public appearances.

Later still, standing on a garage forecourt, she caught a glimpse of the Daily Star. She was front and centre – well, mostly front – in bra and pants. Hang on, she thought, this wasn't the plan. "It was as if I saw myself for the first time. I realised this was all I did for a living. I was so far away from what I really wanted to do and it had to change."

Abi Titmuss. It's her real name and even she reckons the gods were having a laugh that day. She's in on it, though. In her lively new book she dubs herself Lady Titters of North London and Baroness von Tittentrap, after buying a house in Islington. Yet for years it seemed that Titmuss was the joke, a C-list celebrity famous for nothing more than blonde hair, big tits and a willingness to display them while bragging about her appetite for sex. She was quoted saying she was probably perfect for Leslie because, "I am an angel in the courtroom and a whore in the bedroom."

Titmuss is a conundrum. The girl I met a year ago during the Edinburgh Festival defied every expectation. She was – is – prettier than you'd imagine, and nice as pie. They're devalued adjectives, but I'm prepared to rehabilitate them for Titmuss, whose unforced friendliness proved a happy surprise, prompting me to entertain the possibility that she was more than just an opportunist riding to success on someone else's failure.

The Secret Diaries, her record of the mad years in which she mastered the art of "playing the fame game and coming out on top", is part of a programme of reinvention that's seen her starring in the West End, undergoing therapy, and scaling back the suggestive snaps. I'm not sure how effective it will be. My impression – from meeting her, watching last year's interview with Piers Morgan and reading the book – is of a perennial pleaser who wants to be all things to all people without losing her identity, though that's always the first thing to go. And fans looking for an autopsy of her relationship with John Leslie won't find it here. He has a vital supporting role, but the book is really about her time post-Leslie, and all that ensued.

Still, he's back in the headlines, so I probe. She has often expressed her certainty that he's neither violent nor a rapist. Legally, she explains, she's unable to discuss court cases past or present. OK, perhaps she can explain the attraction? She laughs. "If he was good enough for Catherine Zeta-Jones . . . He was extremely handsome, tall, broad shoulders, dressed really well, quite charming and gentlemanly when I first met him."

Leslie asked her to lunch – a new one on her – so she teasingly offered her number: "I'll say it to you once and if you remember it then I'll come out with you." He did, and the rest is infamy. Even so, she says, "He's smart, and a talented pianist. We'd have friends round and he'd play and we'd all sing and it was wonderful."

I'm not a rapist" screamed the head- line, over a paparazzi shot of television presenter John Leslie and his petite, blonde companion as they struggled to navigate from the car to the safety of his house, that December night in 2002. The accusations were heinous, but the blonde, a 26-year-old nurse, vowed to stand by the man she'd been seeing on and off for the past four years.

Studying that picture the next morning, Abi Titmuss worried about how she looked, and about how this would change her life. In The Secret Diaries of Abigail Titmuss she writes, "It's such a weird feeling seeing yourself on the front of a national newspaper . . . the anonymity that we all take for granted, gone with the publication of one headline."

Less than two years later, at 5am on a July morning, Titmuss stepped out into a Hackney street to hail a cab. Anonymity be damned! She was stark naked – bar a pair of Jimmy Choos – and having a blast. How life had changed. She now commanded a small fortune as a glamour model and sometime telly presenter, and earned thousands more making public appearances.

Later still, standing on a garage forecourt, she caught a glimpse of the Daily Star. She was front and centre – well, mostly front – in bra and pants. Hang on, she thought, this wasn't the plan. "It was as if I saw myself for the first time. I realised this was all I did for a living. I was so far away from what I really wanted to do and it had to change."

Abi Titmuss. It's her real name and even she reckons the gods were having a laugh that day. She's in on it, though. In her lively new book she dubs herself Lady Titters of North London and Baroness von Tittentrap, after buying a house in Islington. Yet for years it seemed that Titmuss was the joke, a C-list celebrity famous for nothing more than blonde hair, big tits and a willingness to display them while bragging about her appetite for sex. She was quoted saying she was probably perfect for Leslie because, "I am an angel in the courtroom and a whore in the bedroom."

Titmuss is a conundrum. The girl I met a year ago during the Edinburgh Festival defied every expectation. She was – is – prettier than you'd imagine, and nice as pie. They're devalued adjectives, but I'm prepared to rehabilitate them for Titmuss, whose unforced friendliness proved a happy surprise, prompting me to entertain the possibility that she was more than just an opportunist riding to success on someone else's failure.

The Secret Diaries, her record of the mad years in which she mastered the art of "playing the fame game and coming out on top", is part of a programme of reinvention that's seen her starring in the West End, undergoing therapy, and scaling back the suggestive snaps. I'm not sure how effective it will be. My impression – from meeting her, watching last year's interview with Piers Morgan and reading the book – is of a perennial pleaser who wants to be all things to all people without losing her identity, though that's always the first thing to go. And fans looking for an autopsy of her relationship with John Leslie won't find it here. He has a vital supporting role, but the book is really about her time post-Leslie, and all that ensued.

Still, he's back in the headlines, so I probe. She has often expressed her certainty that he's neither violent nor a rapist. Legally, she explains, she's unable to discuss court cases past or present. OK, perhaps she can explain the attraction? She laughs. "If he was good enough for Catherine Zeta-Jones . . . He was extremely handsome, tall, broad shoulders, dressed really well, quite charming and gentlemanly when I first met him."

Leslie asked her to lunch – a new one on her – so she teasingly offered her number: "I'll say it to you once and if you remember it then I'll come out with you." He did, and the rest is infamy. Even so, she says, "He's smart, and a talented pianist. We'd have friends round and he'd play and we'd all sing and it was wonderful."The early years were good, but as Leslie's success grew, so did their difficulties. "The parties got bigger and wilder and the level of attention put pressure on (us]. Women would be putting their phone numbers in his pocket with me standing right there. Once, we were at a ball, slow dancing. It was the end of the night and I had barely spoken to him because everyone was coming up, sitting on his knee. And of course, no-one wants to speak to you! While we were dancing a woman actually pushed me out of the way. He just let it happen and said, 'They have a piece of me, I'm a public figure.' "

Ah yes, the wild parties. That brings us swiftly to the orgy rumours (not true) and the sex tape (too true), showing Titmuss enjoying carnal knowledge of another woman. Its wide availability remains, she says, the single most humiliating thing in her life. So why make a tape at all?

"When you're in a committed five-year relationship, sometimes you want to have a little fun and spice things up. I don't think there's anything wrong with that. You don't expect someone staying at your house to go through your things when you're asleep and steal it, that's what is wrong! People shouldn't think I made this for public use. It was never intended for anybody else to see it. Was it his idea? Yes. Did I mind? No. Would I do it now? No. I was young. I'd never done anything wild like that, so it was exciting and fun and seemed to be harmless."

Far from harmless, the scandal cost her a job with Richard and Judy. Her manager said, "You're f***ed, basically. In the same boat as Leslie." Then an offer came through for a day's work filming intros for a porn channel. Titmuss weighed up her options. It was loads more than she'd earn in a year of nursing. Her manager was saying she'd never work again, so maybe this was the last hurrah? What did she have to lose?

What was left of her reputation, perhaps? But Titmuss triumphed, becoming the darling of the lads' mags and her career – and bank balance – blossomed. That aggravated those who say she's famous for being famous, not for doing anything. It's a situation Titmuss has been slowly chipping away at; though, as I've said, I'm not sure if the book will help or hinder the cause.

It certainly suffers from the curse of the legal eagles. Trying to read between the lines nearly blinded me. Then there's the lightness of touch, which can mask Titmuss's very real intelligence and thrust her ambition into an unflattering light (though I'm sure if she was a chap, people would applaud her canniness). She wants to be taken seriously, but includes saucy stories that we wouldn't have known if she hadn't told us.

"Just because I've had sex, why does that mean I can't be taken seriously?" she argues. "I wouldn't behave like that now, I have to say. I just wanted to make people laugh. I wanted to show that I'm very different now to how I was a few years ago, but that image of me being a kind of sexy girl wasn't entirely disingenuous. All women have our wild and our sexy side. How people will respond to that, I don't know."

Well, I say, parts of the book make painful reading because she's so self-destructive. Others are uncomfortable because she's breathtakingly honest about her less noble (and often drunken) impulses. While it's not a cautionary tale, her story illustrates what happens when you lose sight of your values and your sanity.

"In that lifestyle, it's very easy to do. I'd go to a tennis match and they'd give you champagne at 10am. It's like that all day and all night." She was once taken off air in a radio broadcast for being too hung-over to speak. "There's that hedonistic side to me. Another part asks: why am I behaving like that? It's not who I really am. It goes back to things in my past. And you're in an environment where there's plenty of drink, drugs are free, and you're in a bit of a strange place yourself."

Strange, but not stupid. Benefiting from sound economic advice, she learned how to work the system by paying for her own glamour and paparazzi shots, then selling them back to the tabloids. Sections laying bare the how-to aspect of celebrity are fascinating. Even as she was mastering the system, it kept getting the better of her naivety. She explains that in the early days, reporters would ask a string of ordinary questions then slip in a few sexy ones in the last five minutes. "I'd react, and that would be the entire thing. In the end I realised that's all they wanted and I embraced that."

Why not stop giving interviews entirely? "I didn't feel that was the solution. Why cut off the hand that feeds you?" For the same reason, she defends reality telly – she's done Hell's Kitchen and Celebrity Love Island. "It serves a purpose. I had some great times. The money's fantastic. They raise your profile hugely and change your career around. Look at Myleene Klass. You wonder why people do it – that's why. Hopefully I can move forward now and do other things."

Those other things mean acting, and one important clarification is that performing is what she's wanted to do since she was a wee girl in Lincolnshire. Titmuss started playing the clarinet aged six, then mastered flute, piano and guitar. When her father, who plays anything woodwind or brass, launched a weekend music school, she sang in the choir. "Music and performing were a big part of my life. I was in all the plays at school and wanted to go to stage school but mum and dad didn't want me to turn into Little Miss Jazz Hands. I used to go to other schools and ask to be in their plays. I set up my own drama club at lunchtime."

After her parents divorced and her father moved to Scotland's west coast, Titmuss "went off the rails". How exactly? "I was a straight A student – ridiculously! In my second year of high school I got an A+ on every single exam and every single piece of work. When you got 100 consecutive As you had to go to the headmaster and get a sash to wear, which I hated. Then my parents divorced and I made the decision not to try so hard anymore. My grades started to slip."

Did she get into any real trouble? "I did get sent home because my skirt was too short one time! By that point I had an older boyfriend in his twenties, and my dad wasn't there and it was a difficult time for us all. I lost interest in school. The boyfriend and the outside life became more important."

She'd been a keen student of Latin and Greek – and recently resumed those studies – but neither they nor drama were A Level offerings at her school, so she started on biology, sociology, French and Spanish.

"Then this boyfriend and I split up and I had a lot of problems with him stalking me." That seems to be a recurring theme, given her problems later with a colleague-turned-stalker who was eventually brought up on charges. "Yeah, well, maybe. I was having to sleep at different houses. At the age of 16, 17, that was very difficult. I wound up leaving the country, to live in Spain. I couldn't cope. It was quite serious. So I left my A Levels, left everything. After a year I came back and thought, what am I going to do now?"

With ten GCSEs she got into university to study nursing, thinking it might offer a way into medicine eventually. In her first week at City University she joined the drama club. After a while, thinking she might make the move to medical school, she got hold of college details, only to realise she was eyeing up schools based on their drama programmes. "I had a real moment, thinking: what is it I really want to do? I was trying to please my parents. I always felt I'd underachieved. Saying I wanted to go to medical school was my way of proving that I could achieve.

"I thought: when had I been happiest? And it was on the stage. I was instantly filled with fear because I realised it was an incredibly difficult profession. My mum said, 'At least carry on with nursing, so while other people are working in bars you can work on the wards. It's a worthwhile job.' But I knew as soon as I graduated I'd want to go back to acting. My mother said, 'If you got into RADA I'd sell the house to pay for it.' That's how much she cared. Parents are amazing, aren't they?"

Sine labore nihil – nothing without hard work, as Titmuss could tell you. She's willing to put in the hours, and thanks to her nest egg, able to start at the bottom. In 2006 she won accolades for her role in Two Way Mirror, by Arthur Miller, and she's doing two more plays in August and October. She is also just back from a celebrity poker tournament in Las Vegas where she went head to head with Matt Damon and Ben Affleck.

She recently celebrated her one-year anniversary with boyfriend Marc Warren, of Hustle fame. What's astonishing, even admirable, is that they've kept it mostly off the radar. A sign, indeed, that she's serious about making changes.

"My life turned upside down and I went slightly mad, too. It was sink or swim and I tried to swim. I was naive, but I tried to make the best of it and embrace it. I never lost sight of what I wanted to do. It was a crazy three or four years, but now I feel more like myself than I have done in years."

Titmuss may have a long way to go before she wins over her detractors, but I, for one, am rooting for her.

The Secret Diaries of Abigail Titmuss is published by Headline, priced £7.99. Titmuss will be signing copies at Glasgow's Borders (98 Buchanan Street) on Tuesday, 29 July, 12:30-1:30pm.