In March this year, 67-year-old music teacher Brian Davey was jailed for 13 years for what the judge called “one of the worst cases of child abuse one can imagine”. Davey had pleaded guilty to 27 counts of attempted rape, gross indecency and indecent assault. Six of the women he had abused as children were in court to see him sentenced; most cheered when he was sentenced. Antoinette Lyons, watching with the others, did not cheer. Brian Davey was not only her abuser but also her stepfather.

She felt hatred for the figure in the dock but pity and love as well. “I found the whole thing very sad,” she says. “Yes, he is a monster. But I’m an incest survivor as well as someone who was abused by my teacher. My overwhelming image is of my stepfather, who in many ways looked after me.”

For Antoinette Lyons, a 32-year-old Cambridgeshire teacher, testifying in public about what was done to her marks a personal liberation after a 20-year silence. Her story - which she has chosen to tell exclusively to Friday magazine -is a moving account of one woman’s endurance and bravery.

It proves that it is possible to live a life after sexual abuse that is full and devoid of shame. And it sounds alarm bells about the failure of the system either to keep abusers away from children or to care for children in distress.

Antoinette (nee Fox) was six years old when she began to learn the recorder at Hugh Myddleton primary school in Islington, north London. She liked the instrument so much that soon afterwards her mother sent her to the White Lion music club, where she was taken under the wing of respected music teacher Brian Davey. A photograph of Antoinette then shows a slight, blonde child with neatly brushed hair and a sweet, winning expression.

Davey first assaulted her in his car, on a trip to buy a new recorder. She was seven; he was in his early 40s. In the years that followed, he abused her countless times, at the music club, at his house - where she went for weekly lessons - and on trips to performances. He touched her intimately, made her perform oral sex and masturbate him and took pornographic photographs of her, sometimes “paying” her with a pound coin. But after confiding in her father following the first attack, Antoinette Lyons kept mainly silent about the abuse for two decades.

She was just one of many victims. Davey was a compulsive, predatory paedophile who used his position of trust in the music community to molest with impunity. He abused girls like a mugger steals - in daylight, in places where people are present but seem not to notice. Witnesses’ testimony reveals that he molested children as young as four - in stock cupboards and staffrooms, at the piano, even in classrooms full of other children. Private lessons provided further opportunities. He took one seven-year-old up to his bedroom promising to show her butterflies then locked her in and masturbated, saying that if she told anyone her already ill mother would die.

For Antoinette Lyons, the nightmare deepened when her parents’ marriage broke up. (Her father, she learned from papers she inherited long after he died, had tried to stop the abuse but had been disbelieved by police, who saw him as the embittered party in a divorce case.) Davey began a relationship with her mother, and moved in with Antoinette, then aged 11, and her mother and younger brother. The abuse intensified but the silence deepened. By this time, she had a scholarship at City of London girls’ school, was a member of Davey’s recorder group and performed regularly. The family moved to Buckinghamshire in 1984 and she continued to do well at school.

“I was a very good girl,” she says. “I spent hours on my homework. I occasionally dabbled in being naughty, going on shoplifting sprees. Then I went back to being extremely good.” On a trip with the recorder group, other girls talked about Davey’s abuse; Antoinette denied it was happening to her.

The tension between silence and speaking out is at the heart of Antoinette’s story. “Silence has not protected anyone and it does not protect children,” she said, after Davey was sentenced. But throughout her childhood she kept quiet, in an attempt to protect people she loved. She says she longed for adults to ask her questions about what was happening to her. Finally, in 1987, when she was 14, someone did.

She was called out of her chemistry lesson at Beaconsfield high school to be interviewed by a female police officer, in the presence of her headteacher and a social worker. A girl from Islington had told her brother what Davey had done to her in the past; his call to the police prompted an investigation, which spread to include two girls in Buckinghamshire. One of them was Antoinette. By this time, her mother had married Davey and had two more children. Antoinette felt it was her responsibility to keep the family together. “I saw myself as a sacrifice,” she says. “That’s my overwhelming sense of my childhood: sacrifice.”

Initially, she denied the abuse to police. Eventually, she admitted that Davey had touched her, and forced her to touch him. But still nothing happened. Her mother, at first unbelieving, was “desperately embarrassed”.

The police advised her mother that it would be better for Antoinette if there was no prosecution. “It would have been considered damaging to drag me through a court case,” says Antoinette. Davey went voluntarily for treatment at the Portman sex offenders’ clinic. He moved into a caravan down the road for a while, returning daily to the family home to give private lessons. (Antoinette had to stay away from the house between 4pm and 6pm while he taught.) Soon afterwards, he moved back in with her mother.

Brian Davey’s case throws a sobering light on the unique position of trust that music teachers occupy. Forced to leave Islington because of persistent rumours about abuse, he had already been suspended from a Buckinghamshire primary school, Butler’s Court, in 1983, following allegations that he molested girls. He was reinstated because of insufficient evidence.

(Buckinghamshire county council launched an inquiry following Davey’s conviction; its draft report is due in July.) Nonetheless, by the late 80s, parents were still queuing up to send their children to him. “Parents knew, girls knew, but no one ever talked,” says Antoinette. Even now, some of Davey’s former associates in music teaching have stood by him; his self-published series of recorder books is still on sale, to the disgust of Antoinette Lyons, who sees the royalties that will accrue to him as “dirty money”.

Davey, whose taste is for small girls, had stopped his abuse of her by the time she reached puberty. But the damage was far from over. Antoinette’s charismatic and manipulative stepfather was a high-profile figure in Buckinghamshire; her reality was at odds with everyone else’s. “Brian was such a pillar,” she says. “Community, family, school - everything was tarnished with him.”

As a teenager, she turned her anger on herself. She began to self-harm, cutting her feet and dousing them in surgical spirit to intensify the pain.

At 18, she tried to kill herself. After the botched investigation in 1987, social services lost interest. She loved school and rarely missed a day.

“School saved me,” she says. “The institution as well as the individuals.

It was an absolute sanctuary.” She told one trusted PE teacher, “bit by bit, over a year”, something of what had happened to her, but with difficulty. “I didn’t have the emotional vocabulary and I didn’t have the sexual vocabulary.”

None of her friends knew. She got As in each of her A-levels in RE, history and English literature and after a year abroad went to Selwyn College, Cambridge, to read philosophy and theology. There, she began seeing a psychotherapist and embarked on the long road to recovery. She never went home, although she continued to be a dutiful daughter, sending Davey Father’s Day cards (this is the first year she has not sent one). She trained at Homerton College and began teaching in 1997.

Meeting Antoinette Lyons today there is little to indicate the trauma she endured throughout her childhood. She has an open, still-sweet face, lives in a cottage not far from Comberton Village College, the 1,000-pupil comprehensive where she teaches philosophy and ethics, and is head of student guidance and a deputy head of year. She is close to her mother - who left Davey a few years ago - and is planning to train as a psychotherapist. She has a child, now nine, from a marriage that lasted five years. She has a two-year-old son with her partner, a PE teacher at the same school, and is pregnant with a third child.

Although Antoinette told her partners bits of what had happened to her, she never told the full story until Inspector Shane Fasey of Cambridgeshire police’s child protection department came calling last year. Islington police had begun an investigation into Brian Davey in 2004, when two women communicating on the Friends Reunited website realised that their former abuser was once again teaching music, and raised the alarm. When officers contacted Antoinette last year to ask her to give evidence, she decided to give it openly. “I didn’t see that there was anything to hide,” she says.

Over the next three or four months she became confirmed in her determination to speak out. She quotes the novelist Margaret Atwood:

“powerlessness and silence go together”.

She agreed to give a statement, thinking it would take an hour or two. It took two weeks, ran to more than 20 pages, and she told Inspector Fasey everything. It was the first time she had told another human being the full story of what Davey did to her. The relief, she says, was “too enormous to put into words. I knew I wasn’t going to die any more. I’d said it, and the sky hadn’t come tumbling down. It was bigger than relief - a physical sense of freedom.”

Not everyone supported her decision. She was advised by Cambridgeshire county council not to speak to the press about the case; they said her family would be hounded and that her own position as a teacher with the authority might become untenable. “I felt I was being persuaded very heavily not to talk,” she says.

It is tempting to see Antoinette’s experience as a throwback from the last century. Schools have come a long way in how they approach cases of suspected sexual abuse; every school now has a named person to deal with such concerns and teachers live in a climate where they might think that false allegations are more common than unreported cases of abuse.

But Antoinette’s story is not from the past. Brian Davey was giving private music lessons until the night before he was sentenced, although he pleaded guilty last October. He was doing so in Cambridgeshire - Antoinette Lyons’s adopted home and the part of England convulsed by the Soham murders in 2002.

Davey moved to Cambridgeshire six years ago. Soon afterwards, in August 2001, Antoinette Lyons called Cambridgeshire social services to express her fears about her stepfather. She was subsequently visited by them and by the police, although at that point she was not ready to speak openly. Davey was also visited by the police.

What Antoinette did not know was that Brian Davey was already working in the county’s schools, having been taken on in January 2001 as a peripatetic music teacher. Her concerns appear not to have been passed on, and Davey continued to have privileged access to children, working in 14 primary schools.

Allegations surfaced again; a child made a complaint in September 2002.

Davey was suspended in April 2003 after another adult saw him touching a girl’s bottom, but reinstated a fortnight later with a warning. Davey was finally sacked in July that year for falsifying his employment record, although he continued to give private music lessons. His name was not added to List 99 - the list of people forbidden to work in schools - until he was imprisoned.

An education official told Antoinette Lyons there had been a “breach” in allowing Davey to teach in the county, describing it as a “cock-up”.

Detective Inspector Mandy Dansey, from Thames Valley Police’s child protection unit, acknowledged at the time of sentencing that: “There is a strong possibility that there are other victims of Davey’s who have never reported their ordeals to the police.”

This week a spokesman for Cambridgeshire county council pointed out that none of the charges for which Davey was jailed related to his time teaching in the county’s schools, but that the council was reviewing the case “to see if lessons can be learned”.

School has continued to be a place of safety for Antoinette Lyons. Children and colleagues have been supportive since her evidence was made public at Davey’s trial. She hopes the stand she has taken will show children that you can live a normal life after abuse, and that speaking out is not shameful. “I’m not out to shock,” she says, “but I want people to hear the reality. It’s what sexual abuse is.”

She loves teaching her subjects, and the pastoral side of her work. “The one thing I wanted people to do, as a child, was ask,” she says. “I make sure I ask questions of kids who look a bit miserable. You can’t afford to be quietly suspicious. You have to act on it.”

Thames Valley child protection unit: 0845 850 5505