By Liz Lewis
BBC News, Gloucestershire
When police burst through the doors of 5 Dunalley Street in Cheltenham it was the end of an investigation meticulously conducted over months.
The raid was part of Operation Pentameter, the first co-ordinated effort to tackle human trafficking on a national scale.
Officers found evidence of links to brothels in other counties and brought three women away from the address.
Police captured the brothel keeper, Ben Lin, 37, six weeks later.
Lin was sentenced to 30 months in jail and recommended to be deported on completion of his sentence.
Operation Pentameter, which was launched by Dr Timothy Brain - Chief Constable of Gloucestershire Police - on behalf of the Association of Chief Police Officers (ACPO), was judged a success for the Force.
Dr Brain has been the ACPO spokesperson on prostitution and related vice matters for more than 10 years.
During his time in that role he has noticed a growth in trafficking women and in some cases minors for sexual exploitation.
"It has been a growing phenomenon and Pentameter was an opportunity to say 'unless we make a stand now this will become a very big problem for the future'," said Dr Brain.
"We needed to make it clear that the UK not only does not support that kind of activity on principle but will also do something about it in practice."
Prior to Pentameter's launch Dr Brain had learned that many forces were indicating through their intelligence that trafficking had ended up in their areas.
"We here in Cheltenham had a case and up the road there was another one in Leamington Spa. My observation to put it simply is if you can get trafficking in places like Cheltenham and Leamington Spa you can get it anywhere," said Dr Brain, speaking as the UK marks the 200th anniversary of the Parliamentary Act to abolish the slave trade.
"That's the reality of this so-called trade we're now engaged in.
"It's something that can start thousands of miles away and end up on a street near you. It is the ultimate international local crime."
As in the Cheltenham case, the majority of trafficked women enter the UK illegally but not through packing crates or packaging, more usually it is by using some form of deception to get through immigration controls.
"The women pay for that to happen and the gang masters get paid and then literally sell the women on, sometimes at the airport, to someone who'll take them on and run them as prostitutes.
"And then they can get sold on again and again - and that quite simply is slavery," said Dr Timothy Brain.
Work carried out in the aftermath of the first stage of Pentameter supports the suggestion women come to the UK for illegal labour but find themselves in sexual exploitation.
One of the benefits of a national approach to the problem of modern day slavery has been a sharing of information between forces.
"We've created a system where that can easily happen - we had a national intelligence cell in London which has turned into something permanent and that's one of the functions of the UK centre for human trafficking in Sheffield," said Dr Brain.
"After Pentameter there is now a permanent body to nationally co-ordinate information and to collate and disseminate specialised intelligence in this field."
The work of Operation Pentameter continues as detectives try to cut off the traffickers' finances.
"The bulk of the profits are in the computer-based offshore accounts that lie behind these illegal criminal activities," said Dr Brain.
"Because they're offshore that presents a big problem for us but equally the same kind of computer financing that makes offshore accounting possible makes it possible for us to trace the assets too.
"That's being handled locally - Gloucestershire police are chasing money banked in China," he said.
The legacy of Pentameter is a tried and tested process in place ready for Operation Pentameter II - again led by Dr Timothy Brain.