Stephanie Davies may be in her late 30s, but there is something a little 'teenage' about the way she describes her ex-husband and the father of her child.

When she discusses Simon Oldham, she tends to use a series of acronyms and shorthand. SXH (Stupid Ex Husband) is a favourite, closely followed by BFL (Big Fat Loser).

Other descriptions are more succinct, but can't be repeated in a family newspaper.

Caught in the net: Steph with her now ex-husband Simon and their daughter Stella

There is a surprising reason for her less-than-mature terminology, though. She confesses that she spent the final months of their marriage perfecting her 'teen speak', as she turned online detective to establish if he was being unfaithful.

Suspicious that her husband of seven years was cheating on her, or at least capable of infidelity, she posed as a much younger - and less eloquent - woman on Facebook called Laura Willsham.

Then she asked Simon if he wanted to be her 'friend'. What happened next destroyed their marriage.

'I posed as a 21-year-old blonde bimbo, so I had to have the language to match,' she explains. 'I'd write them in text speak, or insert abbreviations. I'd even add the odd spelling mistake, just to make it more authentic.'

Well, Simon, 44, was certainly fooled. His replies to his newfoundFacebook 'friend' were flirtatious from the off, and culminated incrude sexual suggestions.

At several points he tried to arrange a meeting with his young admirer, clearly expecting a sexual encounter.

Little wonder his jaw fell to the floor when his wife hit him with the news that his internet 'conquest' was actually her, furiously tapping into her own laptop and raging as she read his suggestive responses.

Today, as the dust settles on their divorce papers, she is still angry. Their daughter Stella is just 15 months old, and Steph is now a single mother.

'Stella was just a few weeks old when this all really started,' she says. 'At the height of it all, I was trying to juggle caring for her and finding out exactly what sort of man her father was.

'Not only did I discover that he was the sort of man who would set up sexual liaisons with a complete stranger, I discovered that he had a whole other life that he was keeping from me,' Stephanie says.

'It wasn't about trapping him. All I wanted to do was find out the truth'

Simon confessed to 'Laura' that he had a wife but also another girlfriend - one, in fact, he has gone on to marry.

'Isent him a message, as Laura, saying "A wife and a girlfriend?" and hejust made light of it. Even that wasn't enough for him, obviously,because he was after sex with Laura, too.

'He made that clear - it was all crude, yucky stuff. I couldn't believe this was my husband.

'Thefinal straw came when I arranged to meet him to discuss our marriage. Iasked him to meet me at 6pm that night - knowing full well that he hadarranged to meet "Laura" too.

'For me, it was the ultimatetest. Would he choose me or her - a woman who didn't even exist? Well,he didn't hesitate. He said he couldn't see me because he had an"important meeting" that night.

'Yeah, right! That was the moment I knew our marriage was over for good.'

Ithas long been accepted that modern technological advances are changingthe way we conduct real-life relationships. Steph and Simon'sexperience shows how dramatic the fallout can be.

Single parent: Steph resents Simon for treating her and their daughter as disposable

Thecouple's wedding photograph, taken in 2002, highlights just what ahandsome couple Simon and Steph Oldham were. Both gregarious andattractive, they were, says Steph, 'known as the perfect couple'.

Butthe fact that Simon had been in a long-term relationship before, onlyto walk out on his partner and a daughter from that union, shouldperhaps have made Steph a little less sure about his ability to be theperfect husband.

'It never occurred to me that my daughter and I would be just as disposable,' she says bitterly.

Steph had worked previously as a nursery nurse, while Simon was a solicitor, but both had tired of their jobs.

Soon after they married - they had met through mutual friends - theybought a hotel together, using Steph's family experience (her parentswere in the business).

For five years, they lived andworked together, 'quite happily'. Steph had always wanted children, butparenthood hadn't happened for them.

In 2007, they turned to IVF and, to their great joy, in the following January Steph fell pregnant.

By May, they decided to leave their home in the Midlands and emigrate to Australia.

'Weloved the idea of the sun and the opportunities there. The only thingthat had been holding me back before was leaving my family, but mysister moved out, too, and my parents came later, so it really waslife-changing for all of us.

'It meant Simon leaving hisfather and brother, not to mention his daughter, but he was fine withthat. He seemed as excited as I was to be starting on this newchapter.'

Simon had secured a place at college on a course that would allow him to retrain as a chef.

The couple rented a house in Queensland and in the October, baby Stella was born.

But it seemed that beneath the surface, Simon was becoming increasingly homesick.

'Hewas talking about missing his family and friends, and wondering if we'dmade a mistake moving,' Steph says. 'I got increasingly cross. We'dmoved for life, and here he was talking about going back after just afew months.

'I was desperate to get him to see sense. Hehad long college holidays due, and I suggested he use them to go backto Britain, to get it out of his system. I guess I thought he'd spend afew weeks, it would rain and he'd soon be on the plane back to us.'

So Simon returned to Leicester, calling and emailing regularly to say how much he missed 'his girls'.

Internet infidelity: It was easy for Steph to be-friend and flirt with her husband using a different identity on Facebook (posed by model)

His absence, and Steph's frequent logging on to their joint Skypeinternet account to chat to him, led to a horrifying discovery, however- namely evidence of messages between Simon and a woman in Australia.

'I knew he'd met this girl at his college before we went back to visitBritain, but I thought she was just a friend. But what I read betweenthem made me realise it was more than that.'

WhenSteph confronted Simon over the phone, he confessed that he had beenunfaithful, but insisted it was a 'one-off' and an 'error of judgment',and he begged for her forgiveness.

'He said she was just a friend, but he'd got drunk one night and it had gone further.'

Simon'sthree-week holiday in the UK became five, six, seven. He told Stephthat he still 'wasn't ready to return to Australia'.

Then came news that he had taken a job in a bar in Leicester.

The bar had a Facebook site, and when Steph logged on she discovered it had Simon listed as a manager.

'That suggests a proper job rather than some filling-in-for-a-few-weeks position,' says Steph.

Simon kept saying he wasn't ready to come back to me and the baby, but that we would work things out.

'The more I thought about it, the more I wanted to know if anyone in the bar knew he had a wife and child.'

So Laura Willsham was born, and a trap was set, although Steph quibbles with that word.

'Laurawasn't about trapping him. All I wanted to do, at the start anyway, wasfind out the truth about what he planned to do with his life. Was hetelling colleagues stuff that he wasn't telling me?'

'It wasn't Facebook that tore my marriage apart, it was my husband. The internet just showed me what he was like'

Ittook only minutes to 'create' Laura. Steph uploaded a picture of adistant relative, who was 21, blonde and pretty, and set up an account.Over the next few weeks she planned to approach Simon's colleagues,hoping to discover more about his life.

'My way in was through this girl called, coincidentally, Laura, who worked at the bar.

'Shemanaged the bar's Facebook site. I asked if she wanted to be my online"friend" and she said yes. When I messaged her, I said I'd been in afew times and liked the place. She didn't question it, or say "Well, Idon't remember you".

'That's the thing about Facebook. No one questions anything.'

Over the next weeks, the two Lauras would chat online.

'One day there was the mention of a life party, and I asked if Simon would be there. And she said, "Why, do you fancy him?"

'I realised this was my chance and said: "Is he single, then?"'

To Steph's horror, the response was not one she had anticipated.

'She told me that Simon had a girlfriend, who was coming over from Australia to join him. I felt sick.

'Later, I discovered it was his college girlfriend. Not only was hedenying the existence of his wife and child, but he was actuallybringing the woman he'd been unfaithful with to the UK - all the whiletelling me we would "work things out". I was devastated.'

Worse was to come, however, when 'Laura Willsham' made direct contact with Simon.

'Itwas his birthday. I sent him a message saying Happy Birthday and hereplied: "Thanks for the birthday greetings - can you remind me wherewe know each other from, as racking my brain, Si."

'A few flirtatious messages later, and Simon asked: 'Do you ever get to Leicester? I need people to distract me for lunch.'

She asked if he was single, only to be told: 'Have gf [girlfriend] but distraction does not constitute infidelity.'

Astonishingly, he started to confide in 'Laura' (ie his wife) about the doubts he had about his girlfriend.

WhenLaura asked if he would tell his girlfriend about her, he said: 'Notbeen together long - odd situation as I imported her from Australia.Not sure if will tell - depends on how lunch goes!'

Inanother email, he confided that his girlfriend - whom Laura assumed wasthe woman he had slept with in Australia - had come to England sixweeks previously, 'but it is not really working and needs to be dealtwith'.

'The man is unbelievable,' says Steph. 'It was onebig sordid mess and he didn't even try to show any restraint about it.He was the one suggesting to Laura that they meet.

'He kept sending crude messages about what he'd like to do to her. It made me feel sick.'

Steph admits her own messages to Simon as Laura were deliberately seductive, and you could accuse her of blatant entrapment.

'You could, but in real life women do go after married men,' she argues. 'It's up to them to say no.'

Having discovered that Simon hadn't told his new friends about her, she had to decide what to do about it.

In April 2009, she and Stella flew to the UK to see Simon, ostensibly to discuss their marriage.

His 'big choice' - the night when he had to choose between meeting his wife or his fictional internet squeeze - pretty much decided all their fates.

'When he chose her, and lied about having a meeting, I wanted to kill him,' Steph says.

'I could not believe he would stoop so low. Not wanting to meet his own wife and the child he had barely seen. All for the chance of some seedy sex with a bimbo. It was the final straw.'

Of course, Simon could never meet Laura because she didn't exist. Twice in their internet 'relationship' she stood him up. Then Steph had to decide how to bring matters to a conclusion.

'The original plan was to confront him outside a bar where he was supposed to be meeting Laura.

'I planned to turn up, chat about what he was doing there, hang around, see him being uncomfortable then say "Oh, Laura's not coming" and walk off.

'In the end, I didn't do that. I was too upset and I thought: "What is the point?" I knew by then that it was over. It came to a head when he made a big thing about renting a flat so we could all be together "as a family".

'I couldn't take it any more and started ranting at him to stop lying. But I never told him that I was actually Laura. I didn't tell him that until a few months ago, when it was all well and truly over between us.'

What was his reaction? 'There was this long silence and you could almost hear the penny dropping. He was flabbergasted, but what could he say?

'Eventually, he managed something like: "Well, you got me there, 100 per cent."'

The pair divorced, bitterly, just after Stella's first birthday, and eight weeks later Simon married the woman from Australia, the woman he had had an affair with and whom he had described to the fake Laura as 'disposable'.

So does Steph now have any regrets about the Facebook experiment that brought her life crashing down around her?

'No,' she says, without hesitation. 'It wasn't Facebook that tore my marriage apart, it was my husband. The internet just showed me what he was like.

'It's a pity I hadn't discovered it years earlier.'