Warning: This story contains details of sexual acts
When Ruth O'Grady reluctantly joined a swinging website, having been persuaded by her husband, she says, she told him she would never have sex in a car with a stranger.
However, within months she was doing exactly that, and filming it to send to him.
She says she had sex with strangers more than 100 times through the website, over an 18-month period.
Ruth says she is traumatised and continues to suffer flashbacks.
She first approached us three years ago and now, after careful consideration, has decided to tell her story using her full name. She wants it to be a warning to other women.
She feels anger towards her former husband, Chris, but she also blames the UK's biggest swinging website. It gave him access to hundreds of men, she says, who he could ask to have sex with her.
The BBC has approached Ruth's ex-husband with these allegations but he did not respond to them.
Swinging typically involves couples meeting up and exchanging partners, but it can also involve just one half of the couple having the sexual encounters.
For eight months, prompted by Ruth's story, the BBC has been investigating the UK's swinging scene. Some people told us they take part because they genuinely want to, but we found this is not always the case.
Ruth says a website called Fabswingers "facilitated the abuse" she experienced.
The site, which has more page views than any other swinging website, and claims to have 600,000 active monthly members, told us consent was the foundation of swinging.
Separately, police forces across the UK have told us the site has been mentioned in hundreds of recent crime reports.
Ruth also says that, while her story is not the same as that of French woman, Gisèle Pelicot - who insisted on a public trial of the men accused of raping her - the subsequent reaction to the Pelicot case has encouraged her to speak out.
"Everyone was so shocked," she says. "I wasn't shocked at all."
From when they met in north Wales in 2008, Chris had often raised the idea of Ruth having sex with other men - but she resisted, she says.
Then, in 2021, after Ruth suffered a mental health crisis, he became her named carer. She was made to feel guilty, she says, that life had not turned out as they had planned.
Her husband brought up swinging again and eventually, Ruth says, she gave in and agreed.
"I know that can sound absolutely barmy to someone just hearing the story, but remember, this isn't overnight. Imagine being with someone for 12 years and them just convincing you of something."
The pair joined FabSwingers and Ruth says she expected they might meet other couples. Instead, she says, the arrangement quickly became something different.
Ruth was having sex with men from the site while Chris watched, waited nearby, or sometimes was not even there.
The meetings happened at their home, or outside in cars, lay-bys or car parks. If she went alone, she says, she was expected to film what happened and send it to her husband.
Within months, she was having sex with multiple men a week, Ruth says, sometimes as many as four in a day.
She did arrange some of the meetings herself, she says, and would appear enthusiastic about swinging, but she now says this was something she never truly wanted to do.
She regularly told her husband she wanted to stop, she says - telling him on multiple occasions that she had been scared and traumatised by the sex.
There would sometimes be a pause, she says, before he arranged more meetings, which Ruth went along with.
Ruth says the encounters took an horrific toll. She contracted sexually transmitted infections, she got pregnant, and while recovering from an abortion she says Chris arranged for someone to have oral sex with her.
"I realised [Chris] really doesn't care about my body or the pain I was going through," Ruth says.
"All these men are abusing my body to the point where it's getting infected, getting unwell, and now this termination is happening, and yet I'm still having to meet these men."
At times, Ruth says it was easier and safer to appear enthusiastic and perform the role expected of her than to resist it - and to get the encounter over with as quickly as possible.
"Some men wouldn't look me in the eye, and some men wouldn't talk to me at all. It's like... I didn't exist."
Looking back, does she consider any of the sex to have been truly consensual?
"No," she says. "I didn't want to be there. I didn't want to be on [the website] in the first place."
Chris was investigated by the police under coercive control and other laws after Ruth made a report, but no charges followed.
Police pointed to instances in the couple's WhatsApp messages where Ruth had appeared enthusiastic about swinging.
Ruth's story raises a central question: how and why can people appear to agree, even enthusiastically, to sex they do not want?
Consent can be complicated, an expert tells us.
"It's quite possible for people to appear to consent to sex they don't want," says Prof Nicola Gavey, from the University of Auckland, who has researched unwanted sex since the 1980s.
Gavey says she has heard similar accounts to Ruth's from other women.
"It can take people time to understand what was happening to them," she says.
We found a man who uses FabSwingers who agreed to speak to us.
Martin, not his real name, has never met Ruth. He says he has used the site for years and has had sex with about 50 people through it, mostly married women whose husbands wanted to watch.
He tries to ensure the women he meets are happy and consenting, he says, but adds there have been times when, once he has entered a room for a meet, something has felt wrong.
More than half the women from couples he has met did not want to take part, he believes.
On one occasion, he says, he saw fear in a woman's eyes when she told him her husband was about to come in and film.
"I should have walked away," he says, crying. "I should have reported it straight away."
In another encounter, he says, a woman appeared to have been "badgered into it". Her husband and another man were encouraging him to continue, he says.
We ask him directly whether, in that moment, he felt like he had been raping someone.
"Yes," he says.
Martin says he believed the woman had been fully consenting up until that point.
Responding to our findings, the website FabSwingers told us that any suggestion that prior online discussion removes the need for in-person consent at the point of an encounter, is not a position the platform endorses, encourages or tolerates.
The BBC submitted Freedom of Information requests to all 45 police forces in the UK, asking for crime reports since the beginning of 2023 in which FabSwingers had been mentioned.
By the end of April 2026, 39 forces had responded - although the Metropolitan Police, the country's largest force, had not.
Their replies identified 329 reports mentioning the site, including allegations of rape, other serious sexual offences, controlling and coercive behaviour, harassment, blackmail, stalking, assault and possession of extreme pornography.
The forces that responded also recorded 26 people as having been charged or summonsed in cases where FabSwingers had been mentioned, with 23 cases ongoing.
The figures for FabSwingers do not mean the site was responsible for what was alleged, and in some cases it may only have been mentioned in the background to a report. However, they show the platform has appeared repeatedly in police records connected to serious alleged crimes.
The BBC did not request information about any of the UK's other swinging websites.
FabSwingers says reports of non-consensual activity are treated as a priority risk and, where it is made aware of them, it acts and co-operates with police if requested.
Ruth is surprised by this response.
She says she reported to FabSwingers banned behaviour by men she had met on the site, including threats made to her of violence or rape, and no action was taken.
Rachel Horman-Brown, a solicitor and honorary KC who specialises in domestic abuse, says Ruth's experience does not shock her.
"There have been dozens and dozens of times over the years that I've heard women complain that they've been pressured into swinging," she says.
Horman-Brown believes swinging can be exploited by abusive partners because, once someone has participated, it can create deep shame, leaving women less likely to speak out.
Swinging can also often involve the taking of explicit photos and videos, which can be very compromising. Horman Brown describes it as potential "ammo" in a relationship.
Groups supporting survivors say similar patterns are reflected in accounts they hear.
At Refuge, the domestic abuse charity, Charlotte Eastop oversees the national domestic abuse helpline and says they hear from women who say they have been pressured into swinging.
Many women are not even sure whether what they are experiencing is abuse, she says, and are not sure how to describe it. "Hopefully Ruth speaking out will have an impact on someone else."
It was while watching an episode of dystopian TV series Black Mirror that was full of "sexual degradation and humiliation", that something clicked for Ruth. Chris had found the episode funny and "I realised - that's what you think about me".
After more than 18 months on FabSwingers, Ruth told him she was quitting the site. But he kept asking her to meet other men again or to try other sexual arrangements.
With outside support Ruth made plans to leave her husband. She moved documents, clothes and money out of the house little by little and a safe place to stay was arranged.
She finally left in 2023, and has not seen or spoken to him since.
But Ruth says she is still deeply affected and extremely nervous now around men. Even taking a shower can trigger memories of preparing for FabSwingers meet-ups.
Why is she telling her story so publicly?
Ruth says even if one woman identifies with her, and realises she is doing things she does not want to do, it would be enough.
If you would like to contact BBC Journalist Catrin Nye about this story you can email her directly on catrin.nye@bbc.co.uk or she is @CatrinNye on social media
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