How often do abusive teacher-pupil relationships occur?
Teacher Jeremy Forrest has been sentenced to five-and-a-half years for abducting a 15-year-old girl and five charges of sexual activity with a child. The case throws light on one of the most difficult crimes to uncover and the complicated nature of pupil-teacher relationships that go beyond the classroom.
Abusive teacher-pupil relationships are given a great deal of prominence in the media.
In 2011, Mark Westcott, 48, of North Wraxall, Wiltshire, was jailed for 16 months after having sex with one of his students. Christopher Drake, 29, of Monton, who called himself the "Salford stallion", was jailed for six years in April in the same year for having sex with under-age pupils.
Incidents are not confined to older male teachers with younger female pupils. Boys are victims too, and female teachers make up a proportion of the offenders.
Female teacher Eppie Sprung Dawson, 26, of Dumfries, is awaiting sentencing for having sex with a 17-year-old pupil.
In 2009, private school music teacher Helen Goddard, then 26, was jailed for 15 months over a sexual relationship with a 15-year-old girl.
Experts freely admit that the real scale of teacher-pupil sexual relationships is nigh on impossible to even guess at.
It's been against the law since the Sexual Offences (Amendment) Act 2000 came into force in January 2001, for a teacher to have sexual relations with any pupil under the age of 18, even if the relationship is consensual.
That applies where the child is in full-time education and the person works in the same place as the child, even if the person does not teach the child. Prior to the act, the age of consent - 16 - was the only issue.
Figures on offences are hard to come by - the Ministry of Justice says it does not collate offences by occupation and the Department for Education did not respond to a request for figures - but it is widely reported that between 1991 and 2008, a total of 129 teachers were prosecuted for relationships with pupils.
Teaching unions say they are rare, with the number of cases that go as far as court tiny, and the number that end up in conviction tinier still.
However anecdotally, it seems to be more widespread. In 2007, a YouGov survey of 2,200 adults found one in six knew of someone who had had an "intimate relationship" with a teacher while at school.
A part of the problem of guessing the scale of the problem is the unique nature of the crime.
Sometimes the victims never complain. Many don't even consider themselves as "victims" until years after the relationship took place. Some never change their mind.
Sarah (not her real name), 37, from Hertfordshire, had a nine-month relationship with her 33-year-old male teacher when she was 16.
"He was the head of department - the young, cool one everyone liked. We had got talking, we got on well. Occasionally he'd give me a lift home from school. Then, two weeks after my 16th birthday he called me into his office and kissed me, saying he'd wanted to do that for ages," she says.
At the time Sarah - who had only kissed a couple of boys before - felt flattered. They later had sex. A fantasy had suddenly become reality, with secret trips to the countryside and nights in together when his flatmate was out. Even though she knew he had a girlfriend, Sarah says she was in awe.
"I thought I was in love and was very up for it - even though he didn't always treat me well. I think some teachers had suspicions, and my friends knew, but I was a good student, and a mature 16-year-old, and we were never found out," she says.
In some ways there's echoes of the evidence that Forrest's victim gave. In court, the schoolgirl, now 16, eloquently defended her former teacher, saying she had "no naivety" about what having a sexual relationship meant.
"It was what I wanted, and I probably encouraged it."
She told jurors they had spoken "a lot" about whether "it was the right thing" as Forrest didn't want to take advantage, and that the plan to go to France was "kind of [her] suggestion".
For Sarah, the court case brought back mixed emotions. Now a married mother of three, she believes her pupil-teacher relationship - which finished after her GCSEs - didn't have a lasting impact on her life, but concedes it could have been different for a more vulnerable 16-year-old.
Looking back, she recognises the relationship was an abuse of power.
"It wasn't until I was pregnant with my first child that I realised how angry I was, or how insane I'd feel if it happened to them.
"I've thought about reporting the teacher - he went on to be a headmaster - but even now, the thought of my dad finding out makes me feel slightly ill. My parents would be absolutely devastated," she says.
At the same time, she says she can't help thinking that if Forrest and the schoolgirl had been left to it, the relationship would probably have fizzled out and they'd both have been fine.
"I find myself strangely hoping he is treated fairly leniently, without really knowing why. I think it's for her sake, that on some level I identify with her," she says.
Sarah isn't the only person that believes pupil-teacher relationships aren't always clear-cut. Prof Pat Sikes, of the University of Sheffield, fell in love with her 22-year-old teacher when she was 14. Now she's married to him.
She's also conducted research into pupil-teacher relationships, which while stressing girls need to be protected against predatory male teachers, challenges the notion all girls are powerless victims.
However for child protection experts, there is no grey area.
Even if Forrest and his pupil, now 16 but 15 at the time of the offences, might believe they have a genuine relationship, it's still an abusive relationship, said Jon Brown, the NSPCC's lead on sex abuse prevention.
Such relationships can become "incredibly confusing" for the victim, whether they are 10 or 15, with all tending to be "left feeling duped, tricked and quite bereft".
Tales such as that of Christina, who says her affair with her teacher, when she was a naive 16-year-old, damaged her for life show some struggle to ever get over it.
Chartered educational psychologist Alan Mclean says fundamentally it's an issue of trust.
"It's an asymmetrical power relationship and the teacher is always the abuser because they are abusing their power, authority and position.
"Teachers are obviously not in a unique position of trust [others include sports coaches, mentors and foster parents], but the point is they are in a position of trust. Trust is the glue that holds everything together and an abuse of trust is rightly seen as a crime," he says.