Frida Farrell hung up the phone to her boyfriend. It was a dry, summer’s evening in 2002 and the 23-year-old was planning to walk home from London’s Oxford Circus to her studio flat in Primrose Hill, a journey that would take about 40 minutes on foot.

As she stepped out of the H&M store where she had been shopping and started headed north, strolling past the BBC building on Langham Street, a man in a grey suit approached her.

The stranger asked her if she would be interested in coming to a model casting. An unusual approach for some, but Farrell, who is originally from Malmo in Sweden, had modelled as a teenager. Although she had moved to London to try and forge a new career – she was studying at the Central School of Speech and Drama – the offer piqued her interest.

“It wasn’t that weird to me,” Farrell, now 38 and a single mum, tells me over the phone from her home in Los Angeles, where she lives with her baby daughter. 

“He was just another photographer.”

Nevertheless, Farrell didn’t say yes immediately, instead taking his business card and agreeing to check his website when she got home.

After reviewing his site she decided it looked legitimate and would be a good way of potentially earning some money. She agreed to an audition the next day.

Arriving at the five-storey building on Harley Street, Farrell entered through a revolving glass door and made her way into a small lift at the end of the hallway to take her up five floors to the penthouse. Walking in to the flat she saw a female assistant, and tables full of coffee, tea and fruit. “All totally normal,” she says. “It’s not like there were dead bodies hanging on the outside or anything.”

After posing for a few photographs, she was sent away and told there would be a callback if the client was interested. About 24 hours later the photographer rang and asked her to return to the same address. He offered £7000 for half a day’s work – enough that Farrell could pay six months rent, but not an unprecedented amount in the world of commercial modelling.  

What happened next changed Farrell’s life forever, throwing her into an underground world of modern sex slavery, which has only grown in the 16 years since her imprisonment.

The estimated number of victims of trafficking and slavery in Britain has risen tenfold from 13,000 in 2013 to 136,000 in 2018. Last year, there were 5,145 cases reported in the UK – the highest on record.

Filled with confidence after scouting out the location the day before, Farrell returned to Harley Street at midday on the Friday for the arranged meeting. It was another warm day and she recalls she was wearing a long brown corduroy skirt and a T-shirt. “I was happy,” she says. That feeling wasn’t to last.

Walking back into the same, small apartment, five floors up, she was greeted by Peter*, the photographer who had spoken to her on the phone. But he was alone. As she stepped into the room, he turned and triple-locked the door behind her, pulling a long hunting knife out of his jacket as he did so. 

“You can barely comprehend what is happening, it’s like suddenly you’re in a movie or something,” she says. “Your whole body goes into shock. I got cold, I got sweaty, everything is moving in slow motion.”

He said nothing so she asked to go to the toilet, hoping to use her mobile to call for help, but he took her bag and emptied her pockets before ushering her into the small bathroom. She stood on the toilet seat and tried to squeeze herself out of a laptop-sized window before remembering she was five floors off the ground and a fall would send her straight on to a concrete-paved garden.

“I was so quiet, barely breathing,” she says. “I’m not going to survive that fall and if I did I would break a lot of bones. What’s worse, the knife or the fall?”

Farrell decided to try and reason with her captor. “Instead of freaking out and screaming, I thought that’s not going to help so I was really calm,” she explained to him she had a stomach ache, hoping he would let her go. Instead he offered her a glass of milk from a fridge in the kitchen.

“He handed me the glass and I thought: I don’t want to drink it he has spiked it. I just looked at him and knew he had, and he knew that I knew, but I just thought I’m going to drink it. I don’t want to feel the knife, I’d rather just drink it.” 

She was then made to put on some used underwear, before she blacked out.

The next thing Farrell remembers is waking up in a different apartment. This location had no furniture – apart from a large bed – no kitchen counters, no doors, not even a lightbulb in the fridge. “There was nothing I could use to attack him,” she says. “You start thinking crazy things like I’ll stand behind the door with a chair like you see in old fashioned comedy movies.”

The new flat was underground, with only small, barred windows up to the street. She tried getting the attention of passers-by but to no avail. When night fell, the lack of lightbulbs meant she was plunged into darkness for hours.

Customers came and went but a heavy cocktail of drugs given to her by Peter meant Farrell was subdued and semi-conscious throughout most of the interactions. She estimates there were more than eight men, but less than 20 paid to have sex with her over the period of time she was kept captive. 

Farrell managed to escape around midnight on the fourth night of her ordeal, after Peter accidentally left the door unlocked while waiting for a customer to arrive.

“I heard him slam the door but not lock it,” she recalls. “I was worried he was playing a trick on me. I opened the door and looked, there was nobody.”

Cautiously creeping up the stairs Farrell noticed she was in the same building she’d arrived at on Friday afternoon, having been moved to the basement flat instead. She ran for the revolving door, fearful of being seen, and didn’t stop running through the streets until she was almost a mile south near Bond Street tube station. She went to a friend’s house where she stayed for days. 

Eventually, Farrell decided to move away from London. Fearful her captors knew where she lived, she felt uneasy living her life. “I used to love going out with friends, drinking wine, going to jazz bars, but it was hard for me to fit in now. What if they saw me and tried to take me away?”

Farrell, who has now produced a film ‘Selling Isobel’ about her experience, says she struggled to come to terms with what had happened over the following decade, carrying guilt and shame about putting herself into that situation. 

“Modern slavery happens all the time,” she says. “If I say ‘sex slavery victim’ to you – you have an image in your head. But any woman or any girl could be kidnapped and put into this situation. Anyone is for sale, you’re just a body.

“They don’t care where you’re from or what you look like. I was just a normal girl, I was like anyone else in my class. It happened to me because I was walking home that night,” she says.

If you suspect someone is a victim of modern slavery you can report them either on the ‘Unseen’ government app or it is free to call the Modern Slavery Helpline (0800 0121 700).