Released: The Taylor girls

Bernard O'Mahoney became Michelle's lover after he helped overturn the sisters' conviction for the murder of Irish bride Alison Shaughnessy (21) in 1992 after just 11 months behind bars. Like many high-profile media campaigners he was convinced of their innocence despite the infamous diary entry which helped convict Michelle of killing the woman married to her lover, John Shaughnessy.

She had written: "I HATE Alison, the unwashed bitch. My dream solution would be for Alison to disappear as if she never existed and then maybe I could give everything I want to the man I love." But within weeks of her release, Mr O'Mahoney says Michelle started displaying the same obsessive attitude towards him as she had towards, John, prior to the murder. In a new book, he tells how he had to fight a new and lengthy legal battle to have his side of the story told.

He admits to deliberately suppressing evidence during the appeal hearing in order to reinforce the sisters' alibis and makes sensational new allegations that, on legal advice, Ireland on Sunday cannot publish.

Mr O'Mahoney, who left his wife and family to become Michelle's lover, believes Michelle Taylor is a cold-hearted, manipulative woman who will stop at nothing to get her own way.

He feels she used him and now bitterly regrets ever having become involved with the sisters in the first place. It was after their acquittal and while he had been working on a book about their case that he and Michelle first became lovers. Mr O'Mahoney says he never meant it to happen; but as far as Michelle was concerned there was no turning back.

She was tired and wanted to get away for a weekend so she persuaded Mr O'Mahoney to accompany her to Colwyn Bay in north Wales where they found a cheap hotel near the sea-front and checked into a room with two single beds. But that night they both got very drunk and slept together for the first time.

"I woke up before Michelle the next morning," Mr O'Mahoney writes in his book. "As she lay beside me, snoring fitfully, fanning her beery breath towards me, I felt like a condemned man waiting for the sun to rise ... When she awoke, she oozed happiness, almost skipping out of bed into the bathroom. I'd never seen her so happy - she was almost cooing with delight.

Most worryingly, from almost her first sentence that morning she was talking as if we were a married couple of long standing - I couldn't face breakfast ... "I hoped that as she readjusted herself to life on the outside she'd come to realise that I was not the man she needed - I was wrong. She became more and more possessive.

In the early days after her release she'd often said how she'd never again allow herself to fall for someone in the way she'd fallen for John Shaughnessy. "But she was lying to herself, because as soon as we'd slept together she'd returned herself to that same emotional landscape; I'd done the deed and now I was going to pay the price.

"I didn't attach the unifying importance to sex that Michelle did; I had a casual attitude to it, which Michelle certainly didn't share." When Bernard O'Mahoney left for work, Michelle would ask him to ring her as soon as he arrived. Often he didn't bother and she would accuse him of lying to her.

"Then when I got home I'd find her pacing up and down the flat, slamming doors and stamping her feet. Before long she'd start shouting: 'You said you'd call. Why didn't you? Who have you been with?'"

At 33 and a doorman who was no stranger to violence himself, Bernard O'Mahoney was an unlikely knight in shining armour. Bearing an uncanning resemblence to Alison's husband, John, he was an underworld "heavy" and debt collector, who ran security at Raquel's club where the Ecstasy tablet that killed 18-year-old Leah Betts had been bought.

Mr O'Mahoney served in the British army for three years and saw a tour of duty in Northern Ireland. He happened to be in the courts when the Taylors' original trial was being held and became a curious spectator. He rapidly became convinced the police had "fitted up" the sisters because he believed there was little hard evidence against them.

Following their conviction, he convinced himself that a major miscarriage of justice had been perpetrated and volunteered to work behind the scenes to create a media crusade designed to get them freed. The British tabloid press had revelled in the sisters' conviction and had little interest in Mr O'Mahoney's claims.

But, partly because of the tabloid stance, the so-called "quality" press lapped up his claims of innocence. Working with the Taylor family, Mr O'Mahoney tried to prove that the sisters could not have driven from Alison's apartment to their alibi at the clinic - where Michelle had worked with Alison and John Shaughnessy - in 11 minutes.

Most drives he took on the same route only proved that the police timings of 11 minutes were correct - but he still recorded that it took 15 minutes and more. These false timings were accepted by the quality papers and by broadcast journalists.

Mr O'Mahoney's campaign hinged on claims that Michelle was convicted on her morals, that jewellery was stolen from the flat (suggestive of a burglar) and that a Home Office pathologist said he'd never come across a case in which a woman had inflicted so many stab wounds.

Mr O'Mahoney then tried to pin the murder on a new suspect, a homeless man who was allegedly ignored by the police in their original investigations. However, their run of good fortune ended on the day before the start of the appeal. A headline declared: "Sisters setback in Alison appeal."

The report stated: "A witness was said to have told how he heard a tramp say he had killed a woman at the time of Alison Shaughnessy's murder. But he has refused to go to the Court of Criminal Appeal to speak for Michelle and Lisa Taylor after saying his story was misunderstood.

"The man, said to have been working in a soup kitchen when he heard 'the confession', gave police a sworn statement saying he did not believe the tramp had anything to do with the killing." Mr O'Mahoney admitted: "I'd known the 'homeless man' yarn would collapse under any serious prodding, but we'd prayed that the collapse wouldn't take place until after the appeal."

In any case, the murder verdicts were quashed, partly because the original press coverage was deemed to have been prejudicial and partly because the defence was denied access to information of a prosecution witness given in an earlier police report. Nevertheless, the police immediately announced they wouldn't be re-opening the case and weren't looking for anyone else in connection with murder.

After the appeal, Mr O'Mahoney returned to the Taylors' south London home to celebrate but told Michelle he couldn't stay. She expressed disappointment. The following day he told his partner, Debra, that he was about to write the Taylors' book. They rowed and Mr O'Mahoney left his home.

He stayed with the Taylors, sleeping with Michelle, but they didn't have sex. An uncle provided a flat in nearby Brockley. Mr O'Mahoney moved in with Michelle hoping to quickly finish the book. They first had sex during their trip to Wales. Their relationship deteriorated as Michelle demanded more than he could give.

The Taylors spent 30 months in the courts attempting to block the publication of Mr O'Mahoney's book, The Dream Solution. This week he told Ireland on Sunday: "It is all very sickening and very hurting for Alison's family. Her father, Bobby, and mother Breda are living back in Piltown, Co. Kilkenny. All the cases have been very upsetting for them.

What more can I say to them but 'sorry'? "Two weeks after I split from Michelle she started phone pestering my partner, Debra, the mother of my children." Mr O'Mahoney has now lost his family "because of the Taylors". He says: "I am that sort of person, once I get into a thing I don't let it go."