Vietnamese children forced into slave labour in UK's clandestine cannabis plantations
Vietnamese boys and young men forced to commit crimes by cultivating drugs in clandestine plantations controlled by ruthless traffickers
UK criminal defence lawyer Philippa Southwell points to the thick ring binders that line her desk in a small office above a bookie's and fast food joint in south London.
More folders are neatly stacked on the floor, in a bookcase and a metal filing cabinet, a hint of her growing caseload.
In recent years, Southwell has specialised in representing a particular kind of client: the young men and boys who are trafficked to Britain from Vietnam to labour on illegal marijuana farms.
Often from poor families, many regard the West as a gateway to prosperity. Others leave weighed down by a duty to provide for parents, brothers and sisters back home.
The Home Office estimates there were up to 13,000 victims of slavery in Britain in 2013. Victims are most often from Albania, Nigeria, Vietnam and Romania.
Many of the Vietnamese are children when they set off, travelling thousands of kilometres by foot, boat and lorry over months, sometimes even years, before reaching British shores.
"They will be trafficked usually through Russia, Germany, France. Some of it is done by foot through the woods for days. They sleep in makeshift camps and then they're made to hide in the back of vans in quite squalid conditions," Southwell said.
"They have to remain quiet. They can't move, there is no air. They'll have to urinate in the box they're hiding in."
Once they arrive in Britain, the youngsters are kept as virtual prisoners by their traffickers and forced to tend to cannabis plants in houses rigged with complex heating systems and high-powered lights to pay off their debt, which can be as much as £30,000 (HK$360,000).
"It's very dangerous. The electricity's been tapped, there're wires everywhere. The windows are almost always nailed shut so they can't leave," Southwell said.
"There are filters over the windows so the light can't come in."
When Vietnamese workers are discovered, often during a raid, they are treated as criminals not victims, campaigners say.
"To my knowledge, there's never been a prosecution of a Vietnamese trafficking gang for bringing children in for this purpose," said Chloe Setter, head of advocacy, policy and campaigns at ECPAT UK, a charity working with trafficked children.
"We've actually locked up, prosecuted and convicted more victims unlawfully than we have prosecuted those that are exploiting them," she said.
In 2013, the Lord Chief Justice of England and Wales ruled that victims of the "vile trade in people" should not be prosecuted when he quashed the convictions of three Vietnamese men, including one of Southwell's clients, for drug offences.
But little has changed since then, experts said.
The police are still arresting minors caught cultivating cannabis while failing to search for clues that might lead to the trafficking ringleaders, Setter said.
For example, they rarely investigate numbers in the mobile phones frequently confiscated from the cannabis gardeners.
Duty solicitors called when a minor is detained still advise them to plead guilty to drug-related charges without recognising they might have been trafficked, Southwell said.
As a result, she is busier than ever, trying to overturn convictions and stop prosecutions.
In 2013, the British government announced the Modern Slavery Bill, which is expected to be passed before national elections in May, and acknowledges that victims of trafficking may be have been compelled to commit criminal offences.
Though subject to change, the bill in its current form gives trafficking victims who have been forced to commit certain crimes a defence in law.
Campaigners say, however, such victims should not be prosecuted in the first place.