When 24-year-old Karyna* met her new boyfriend on a dating website, she thought he could offer her everything she was looking for in a relationship.

Well-spoken, well-educated, with two degrees and a career in web design, 28-year-old Ben* was sweet and attentive, sending her good morning texts and planning romantic dates. So Karyna, a graphic designer, believed the first time they made love after six weeks of dating would be a tender expression of their feelings for one another.

Instead, as they became passionate, Ben’s hands reached up to Karyna’s throat and he started to squeeze. She recalls: ‘Instantly, I thought: “I’m going to die.”

‘I panicked and tried to peel his fingers from my neck. But he wouldn’t let go and kept pressing. His face had changed, too. He stared at me with a look of disgust. I felt completely helpless and burst into tears. At that point, he seemed to realise what he was doing. He snapped out of this strange persona he was acting out, released his hands and said: “What’s wrong?” ’

British backpacker Grace Millane, 22, (pictured) was strangled by a man she met on Tinder, experts revealed their views on the rise in extreme violence during consensual sex

But despite Karyna’s clear and repeated requests for Ben never to choke her again, over the next few months his hands kept creeping up to her neck. He also tried slapping her around the face.

‘I’d say to him: “Please, I’ve asked you not to do that. If you love me, as you say you do, why inflict pain?” He’d say: “I’d never hurt you. You need to trust me.”

‘He’d tell me I should want to let him do it, to make him happy. He’d add that plenty of women liked it, and if I didn’t, he’d find other girls who did.’

A few years ago, it would have sounded like a terrifying brush with a sexual psychopath. Yet Karyna’s experience has become increasingly common.

A BBC survey on the subject this week found a third of women under 40 have experienced unwanted acts of choking, slapping, gagging and spitting during consensual sex.

When I typed ‘choking’ and ‘strangling’ into Google, I was confronted with thousands of clips showing men with their hands around women’s necks.

Others showed hands pressed over women’s noses and mouths, or ligatures, such as rope or ties, around their necks.

In many more cases, I saw women gasping for breath or passing out. In one easily discovered clip, I saw a young woman kneeling on a bed, being pulled up by a noose, hanging from a rafter, that went around her throat while a sex act was performed on her.

Another scene showed a woman being strangled with a rope and left for dead, her face puce. Moments earlier, she had told the man pulling the rope that she ‘liked’ it.

While it is true some people enjoy sa do-masochistic sex, in the videos I saw, many women had tear-stained faces, often contorted in pain and fear.

Hannah Pearson (pictured) was strangled at age 16, by 24-year-old James Morton who had watched strangulation videos and had choked previous partners

There are those who say this is all just play-acting, despite the research showing how porn-makers often exploit women who are abused.

But just to make it clear what these clips are really about, they are captioned with titles such as ‘Slut spat on, slapped and choked’. Teen girls are particularly popular subjects, with videos called ‘Teen choked’ or ‘Choke me Daddy’.

The rise of violent porn also appears to have handed men who are already violent or misogynistic an easy excuse for murder, as in the recent case of Grace Millane, the British backpacker who was strangled by a 28-year-old man she had met on Tinder.

Her murderer falsely claimed the 22-year-old had died in a ‘sex game gone wrong’. After her death, he went online to look for violent porn.

It’s beyond belief — and yet her death is just one of 59 UK cases highlighted by the campaign group We Can’t Consent To This, in which men have given ‘rough sex’ as their defence for killing women. Some had no charges brought or were acquitted.

Karyna is in no doubt where her boyfriend, Ben, got his obsession with choking: the violent internet porn he had consumed since his teens.

Boys grow up thinking violent sex is the norm

‘He was proud of how much porn he watched,’ Karyna says. ‘He’d message me pornography at work, although I had asked him not to.

‘When he wanted to choke me, he’d say: “This is what girls do in porn.” It was like normal sex was too boring.’

After a year of Ben refusing to respect her wishes, Karyna ended the relationship. ‘It was too terrifying. If he’d decided to keep squeezing, I would have been dead. My life was literally in his hands.’

The practice of inflicting pain during sex is not new; the Marquis de Sade wrote about it in the 18th century. Auto-erotic asphyxia has long been used to increase sexual excitement by restricting oxygen supply to the brain.

But while sado-masochism has always been a niche interest — and is governed by strict safety rules, including agreeing beforehand what will happen, ensuring all parties consent and using ‘safe words’ in case any participant becomes uncomfortable — throttling is now not only part of mainstream porn, but also mainstream sex.

Helen Walmsley-Johnson (pictured) feared that she would die during sex and would pretend to pass out to make her ex-boyfriend stop strangling her

In a crowded market, porn sites are showing ever more extreme practices to get clicks. And, terrifyingly, this multi-billion-pound business is often the most powerful form of sex education for today’s youth.

In a content analysis of the most-viewed porn films for the journal Violence Against Women, researchers found 88 per cent contain physical aggression, including gagging. Women are the targets 94 per cent of the time. According to the study, ‘targets most often showed pleasure or responded neutrally to the aggression’.

Astonishingly, choking or strangling is likely to be one of the first sex acts a child sees when they view porn for the first time — which they are doing at an increasingly early age.

In the UK, half of 11 to 16-year-olds have seen online porn, according to a study by Middlesex University. The same study found 44 per cent of boys say it has given them ideas about the type of sex they want to try — and that, over time, young people become ‘desensitised’ to violence.

The sooner boys start seeing this material, other research suggests, the more likely they are to treat girls like objects on whom they can act out what they have seen, regardless of the pain it causes.

And with no disclaimers telling naive youngsters that this is not how the majority of women want to be treated, they start to believe it is.

Professor Gail Dines, a British-born academic living in the U.S. and author of Pornland: How Porn Has Hijacked Our Sexuality, has spent 30 years studying the subject. She says: ‘All these practices sound extreme, but these are what an 11-year-old boy sees when he first puts “porn” into Google.’

‘We know strangulation and choking are among the most popular acts seen in porn.’

Worryingly, she adds that simply seeing such behaviours can alter a young person’s sexual tastes.

Paul, 23, from Hertfordshire, chokes his partners without seeking consent first as he enjoys the combination of giving pleasure and fear (file image)

‘The younger they are when they see it, the more it’s going to get seared into their sexual template. So now, a lot of young men are playing out porn sex. Women are the collateral damage of the porn industry.’

During my research, while I heard from young men who would never dream of strangling their partners and are shocked by the trend, I also heard from many who defended the practice as ‘normal’.

One such man is 21-year-old Felix*, from Brighton, who says viewing porn from an early age has helped form his ‘sexual identity’. ‘Watching porn helped me develop an interest in the more extreme stuff. Any “vanilla” type straight sex is just dull.

‘One of the first girls I had sex with asked for it, and I found it turned me on, too. Now I’d only seek out girls who are into the same things.’

Marketing manager Paul*, 23, also defended choking — without asking his partner first — as a sexual practice.

Paul, from Hertfordshire, admits one girl ‘freaked’ out when he tried it, a reaction he blames on the fact she was a virgin. Even so, he says he still does not seek consent first, and if the woman doesn’t move his hands from her throat, he continues.

According to Paul: ‘It’s just pretend. I enjoy the combination of giving pleasure and fear. My girlfriend enjoys it, too.’

I pretended to pass out to get him to stop choking me, but he soon got wise to that - Helen Walmsley-Johnson

It seems many of today’s young women are caught in a perfect storm: sex with men reared on violent porn; a crisis of self-confidence that they can never do enough sexually; and a hook-up culture which means if they don’t agree to a certain sexual practice, the next date will.

One such woman is charity administrator Joanna*, who was choked by a man she had been dating for a few weeks.

‘He could see on my face I didn’t like it, but I brushed it off because I felt naive,’ she says. ‘My priority was pleasing him.

‘I thought: “Are my tastes too boring? Is this what people do?” ’

Joanna, 29, has watched porn regularly since her mid-teens and says she finds videos of women being choked ‘degrading’. However, she admits she allows her current partner to put his hands around her neck, saying it makes her feel desired and ‘as if he will do anything to have my body’.

‘I don’t think it’s the act which is the problem. It’s the lack of consent,’ she says. ‘I enjoy the feeling of not being in control.’

Helen (pictured) believes her ex partner would've said it was a sex game gone wrong, if he had killed her during sex

Porn expert Professor Dines points out: ‘Porn not only teaches men about dominance, it teaches women about submission.’

It has not helped, she adds, that strangulation has been euphemistically re-branded as ‘breath play’ and touted as a new type of risqué sex by women’s magazines. The novel Fifty Shades Of Grey also romanticised S&M culture.

‘If you are a young girl growing up in a heavily pornified world, you are going to feel it’s normal for you to want those things.’

However, choking features in 16 per cent of domestic violence cases in which women need hospital treatment. Its use in sex dangerously blurs the line between experimentation and abuse. One woman who feared she would be killed by a partner who throttled her during sex is Helen Walmsley-Johnson.

When I spoke to her this week, her voice was rasping, a consequence of being regularly choked, which caused permanent damage to her throat.

Helen says her ex, Franc*, a French businessman, used strangling during sex as a threat.

‘At first, I pretended to pass out to get him to stop [choking me]. But he soon got wise to that and would do it regularly to make me do what he wanted.

‘People talk about strangulation as a type of sexual pleasure, but I found it terrifying.’

Helen, who documents her experiences in her recent book Look What You Made Me Do: A Powerful Memoir Of Coercive Control, ended the relationship when Franc moved abroad for work.

Now, she says: ‘If he had killed me, he would have said it was a sex game gone wrong. From my own experience, I would say to any woman: don’t do it.’

Wendy Murphy, Professor of Sexual Violence at the New England Law School, believes because sex is involved many fail to see strangulation in porn as extreme violence (file image)

Indeed, campaigners say we are in urgent need of a reality check. The tragic number of women killed in what men later claimed were violent games gone wrong offers compelling evidence of this.

Grace Millane is one of them; another is Charlotte Teeling, 33. After 41-year-old Richard Bailey met her in the street in February 2018, he strangled her during what he claimed was ‘rough sex’.

Another man, Ashley Foster, 24, searched online for porn videos about schoolgirls after strangling Meghan Bills, 17, during sex at a Birmingham hostel in 2017.

Schoolgirl Hannah Pearson was only 16 when she was strangled by 24-year-old James Morton in his bedroom in Newark, Notts, in 2017. The jury heard he had watched strangulation videos and had choked previous partners.

Yet even though there are laws against extreme pornography — introduced after the murder of 31-year-old teacher Jane Longhurst in Brighton in 2003 by a man obsessed with it — such legislation is rarely used.

According to a new study in the Journal of Criminal Law, the vast majority — 85 per cent — of prosecutions linked to extreme porn are for sexual attacks on animals (bestiality), not on women.

Wendy Murphy, Professor of Sexual Violence at the New England Law School, says the fact sex is involved prevents many from seeing strangulation in porn for what it is: extreme violence.

Wendy says: ‘If you beg your neighbour to come and hit you with a baseball bat because you insist you will really enjoy it, your neighbour will still go to prison. The same should apply to strangulation.

Fiona MacKenzie, founder of the We Can’t Consent To This campaign, argued that the pressure for women to go along with the violence shouldn't be underestimated (file image)

‘We wouldn’t tolerate this sort of violence against animals, so why do we tolerate it against women?’

Unless we take action now, Wendy says there will be many more cases in the future.

‘We are training our children to think that sex is violence. In boys, that trains their brains to respond to violence with an erection. Then the body starts to want the violence in order to feel pleasure.’

Fiona MacKenzie, founder of the We Can’t Consent To This campaign, says it’s essential to bring the subject into the open.

‘We are hearing a lot from young women who have been choked without consent and gone along with it, pretending to enjoy it.

‘I would not underestimate the pressure on women to go along with this.

‘I don’t believe the men who do this are always bad. But I do believe many are being coached by porn into doing stuff that overrides their knowledge that strangling is extreme violence.’

A year on, Karyna is not only deeply traumatised by her experience, but also worried for other women.

‘It makes me feel sick knowing that my ex-boyfriend will be doing this to other women. ‘I wouldn’t want any other woman to fear for her life as much as I feared for mine.’

How to talk to your child about porn Professor Gail Dines, of Culture Reframed (culturereframed.org), offers this advice: Don’t delay. You can start conversations with your child at any age as there are age-appropriate ways to discuss most topics. They are very likely to find explicit content sooner or later, so they’ll be better equipped to cope if you’ve talked to them about the existence of pornified images and videos.

Turn to tech for help. Filtering apps such as Safe Surfer and computer programs like McAfee Safe Family can block porn sites much of the time.

Keep the conversation going. Let them ask questions, so they know they won’t get in trouble if they talk to you about watching porn.

Encourage them to question what they see. Explain that the people in the videos are actors, and their behaviour is not typical of real relationships.

If you discover your child has watched porn, don’t make them feel ashamed, as this will stop them confiding in you. Talk to them and find out if anyone else was involved before deciding what to do next.

Seek outside help. The organisation Culture Reframed (culturereframed.org) has developed a set of tools for parents to help them advise their children. Advertisement

* Some names and details have been changed to protect identities.

Tanith Carey is the author of Girls Uninterrupted: Steps for Building Stronger Girls In A Challenging World.