'I was trafficked into UK prostitution'
Nearly 800 women and girls working in the sex trade were identified as the victims of human trafficking last year, according to National Crime Agency figures seen by the Victoria Derbyshire programme.
Organisations working with victims, including the Poppy Project, say the figure underestimates the scale of the problem and has been rising sharply in recent years.
It is a fate experienced by Ope, 24, who in 2005 met a man offering to help her leave her life in Nigeria and find employment abroad.
Her role, he said, would be as a nanny, or in a factory. She did not realise she would be forced into prostitution.
Following a treacherous four-day trip by boat, with little food or water, she arrived in Madrid, Spain, where she was put to work on the streets.
But after becoming the victim of rape, she was transferred to the UK by her traffickers. "It was like I was a slave," she says, on the work forced upon her.
One day, while being allowed to buy food in the market, she found a lost wallet containing identification. Taking money from her traffickers, she decided to run away.
But when she boarded a train at King's Cross St Pancras in London, Ope was stopped by an immigration officer and later sent to HMP Holloway.
While in prison, she was helped by the Poppy Project charity, before she was recognised by the court as a victim of human trafficking.
All criminal charges against Ope have now been dropped, but she may have to return to Nigeria, where she fears being re-trafficked.
Ope's name and some details of her story have been changed for her own protection.
Interview and animation by @jim_reed, artwork by Jesse Brown.