Rochadale: Inside one of Britain`s biggest special anti-trafficking operations, police officers surrounded by files, forms and photographs attempt to unravel a complex network of crime.
On a whiteboard, the faces of men, women and children are encircled by a web of ticks, checklists and scribbled diagrams with names, addresses and nationalities scrawled in black.
Operation Retriever was set up in September after police in northern England were alerted to a Slovakian woman who had been tricked into travelling to Britain and then forced to marry a man threatened with deportation back to South Asia.
The woman had been sold for thousands of pounds by a trafficking ring in a case that sparked alarm about slavery in modern Britain and the scale of the hidden problem.
"Modern slavery is not (being chained up)," said Detective Inspector Jim Faulkner, who leads the team at Greater Manchester Police, the largest force outside London.
"It`s being coerced and feeling compelled to work somewhere because the victims think they have no other choice and the traffickers have such control that they live in fear."
Since the Slovakian case, his seven detectives have uncovered eastern Europeans trafficked to the UK for forced labour in factories and many more in sham marriages.
There are as many as 13,000 victims of slavery in Britain, forced to work in factories and farms, sold for sex in brothels, or imprisoned in domestic servitude, among other forms of exploitation, according to the Home Office (interior ministry).
In response to the problem, the government announced in 2013 a draft bill which would raise the maximum penalty for traffickers to life imprisonment. The Modern Slavery Bill is widely expected to be passed before elections in May.
Faulkner`s team is based in Rochdale, a town in north England once at the heart of Britain`s textile industry.
Today it is known for being at the centre of a 2012 sex trafficking scandal in which nine men of Pakistani, Bangladeshi and Afghan origin were jailed for a total of 77 years for abusing dozens of girls.
The men groomed the girls with gifts, and plied them with alcohol and drugs, before forcing them to have sex with others. The scandal was followed by similar cases in other towns.
"In terms of the wider national picture, we know human trafficking is taking place in every town, in every major city in the country. This is a wide-scale problem, with a lot of money to be made," Faulkner told the Thomson Reuters Foundation.
One officer, who asked to remain anonymous, said human trafficking was more lucrative than the drugs trade, and that, given the complexity of the crime, criminals were more likely to get away with trafficking people into Britain than drugs.
The International Labour Organisation estimates that globally, millions of forced labourers are generating some $150 billion a year in profits for those who exploit or enslave them.
For some victims, a life of forced labour and the income it provides - no matter how pitiful - is preferable to a life back home with no money at all, some experts say.
For the police trying to bring perpetrators to justice, the reluctance of many victims to speak out against their traffickers is a major hurdle preventing more prosecutions.
Campaign groups say the reason why trafficking is under-reported is partly because victims are too afraid of their traffickers to provide evidence against them.
Faulkner said he was well aware of the problem, which is complicated when victims do not realise a crime has been committed against them or that enslavement is illegal.
"These are some of the most vulnerable people you can meet, and the process takes time ... the initial contact is stand-offish and distrustful," he said.
Victims of trafficking from eastern Europe often have little confidence in the police, Faulkner said, adding that many came from countries where police forces are perceived to be corrupt.
"You can`t pursue a someone you know nothing about, you need the victim for that information," he said.
"Only when you delve into the history, and build a relationship, can you find out what has actually happened."
This approach led to the operation`s defining moment - a raid on a factory in which 20 people were rescued.
The victims from eastern Europe had been paid only 25 pounds for working 80 hours a week in a picture frame factory.
"I remember walking into that factory, explaining that we were police ... We had people running towards us in tears, and saying `help me`. They were clinging to our arms and some had to be carried out," Faulkner said of the raid in December.
While the police get to grips with tackling slavery, becoming increasingly aware of the warning signs, hotspots and sources of intelligence, criminal strategies are ever adapting.
Despite pressure from the Home Office to increase convictions for trafficking, Faulkner said each case needed to be dealt with according to the victim`s needs.
"Fundamentally we are there to protect them from harm," he said. "I`m quite happy to walk away from a case in order to safeguard the victim."