Britain has become a destination of choice for a new and terrifying global trade - young girls from poor countries enticed into the country and then forced to work as prostitutes. BBC Radio Five Live investigated the trade.
Julia, a 21-year-old from Albania, speaks softly as she describes her ordeal and keeps her eyes on her lap.
Women smuggled into the UK are often forced into prostitution
She was brought up in a remote part of northern Albania.
Her father spent his wages on drink and her mother had to sell her own blood to feed the family.
One day a cousin visited Julia's house and unexpectedly asked for her hand in marriage.
The smartly dressed man with a flashy car promised they would start a new life together abroad.
Sixteen-year-old Julia was a bit nervous of the smooth-talking stranger, but she was also desperate to escape from a life of poverty and from her alcoholic father.
A few days later she discovered there was to be no honeymoon - the man she thought was her fiancÚ was really her pimp and trafficker.
She was taken to Italy and, after a few months "apprenticeship" on the streets of Milan, was sent to the UK in the back of a lorry.
Almost immediately she was put to work in a squalid flat in London's West End, servicing up to 20 men a night.
Whenever she complained she was tired, her pimp beat her or cut her with a knife. Her body is covered with scars.
"He got very angry with me and said I must work harder, make more money," Julia said.
She was trapped in this living hell for nearly five years, afraid the pimp would kill her if she tried to escape.
She was scared of reprisals against her younger brother and sister.
Asking punters for help got her nowhere, but going to the police was out of the question - she feared they would instantly deport her as an illegal immigrant.
She only escaped when a brothel maid, appalled by her bruises, offered her shelter in her own house for a week.
The police say up to 1,400 women a year are brought into the country illegally to be prostituted and that the trade has become as lucrative as drugs.
"Once the girl is worn out or she is infected by some sexual disease she is cast aside, just as you would with a fridge or a washing machine that was broken," said Superintendent Chris Bradford, head of the Metropolitan Police's Clubs and Vice Unit.
"They are nothing more than a commodity," he said.
Police have in the past been criticised for failing to investigate the crime of trafficking.
Clients will not help women forced to work as prostitutes
Foreign women picked up in brothel raids are sometimes handed straight over to the immigration authorities and deported.
But police say they are on the lookout for trafficking victims.
I follow plainclothes officers from the Clubs and Vice unit, as they "visit" flats and saunas in the West End.
Last month trafficking for sexual exploitation was made a crime punishable by up to 14 years in prison.
That may deter traffickers in the future but what about their victims?
Finally there is a scheme to help women like Julia.
She is living in a safe house far from the part of London where she worked as a prostitute.
She is going to college, learning to read and write in English and is hoping to train as a hairdresser.
Julia is part of a new pilot scheme launched in March this year called the Poppy Project.
Government balancing act
It is funded by the government but run by a women's housing association in south London.
Trafficked women who are referred to the project receive assistance including safe accommodation, health services, counselling and immigration advice.
In return they are expected to co-operate with police to help convict more traffickers.
The government is involved in a tricky balancing act.
On the one hand it wants to show compassion to victims of this crime and help them rebuild their lives.
On the other hand there is strong pressure to cut the number of asylum seekers and crack down on illegal immigration.
But women like Julia are stuck in the middle, fearful of retribution if they are sent home - or if they stay and testify against the men who forced them into prostitution.
Julia's story is told on the BBC Radio Five Live Report:
Trafficked and Trapped on Sunday 7 December at 1930 GMT.