Q and A: Modern slavery in the UK
Police are questioning five people over allegations of slavery after 24 people were found allegedly held against their will on a traveller's site. The case is unusual - but is slavery a hidden problem in modern Britain?
What are the facts behind the case in Bedfordshire?
Detectives say they have freed 24 people who were being held against their will, living in filth and cramped conditions. Some of the men had been held for up to 15 years - but others just for a few weeks.
Is this case unusual?
Most forced labour investigations have focused on the trafficking of women in to the sex trade in the UK. The Operation Netwing arrests in Bedfordshire are something different.
Fifteen of the men who were found living on the site were British citizens. The others mostly came from Poland, Latvia and Lithuania. In that context, the investigation is very unusual.
What are the offences at the heart of the investigation?
The investigation has looked at alleged crimes under Section 71 of the Coroners and Justice Act 2009. This act, which came into force in 2010, created a new offence of holding another person in slavery or servitude or requiring them to perform forced or compulsory labour.
Prosecutors have to show that the suspect knew or ought to have known that the victim was being held or forced to work against their will.
Why did Parliament need to create anti-slavery powers in 2009?
There was no single offence that fully covered the crime.
The slave trade was abolished and outlawed in the 19th century. Once that happened, a slave-holder could be prosecuted for a range of offences including false imprisonment, assault and, in more modern times, for breaching specific employment regulations such as health and safety.
In 2004, Parliament created a specific offence of trafficking someone into the UK for forced labour.
North London woman Saeeda Khan was believed to be the first person convicted under that law when a jury found her guilty of trafficking a Tanzanian woman into the country to work as her domestic slave.
But if a criminal forces a victim already inside the UK or from the EU into servitude, they cannot be prosecuted for trafficking. So the 2009 Act set out to recognise forced labour as a crime on its own - making it theoretically easier to bring prosecutions. The Bedfordshire operation is the biggest to date and a sign that detectives think the law can deliver results.
So what do we know about the numbers?
The best official figures come from the UK Human Trafficking Centre, part of the Serious Organised Crime Agency.
It says that in the two years until the end of March 2011, it received 1,481 reports of suspected trafficking. The top three nationalities of victims were Nigerian, Chinese and Vietnamese. British citizens were also in the top 10.
Women made up almost three quarters of the suspected victims - and half of all the cases related to allegations of sexual exploitation. The other half all related to forced labour - with more than 200 involving allegations of people being kept as domestic slaves. Some 50 people aged between 17 and 12 were found to have been abused in the sex trade. Two children under 10 were found to be working in forced labour.
Anti-Slavery International, a charity, says its best guess is that there are 5,000 people in some form of forced labour in the UK - but this figure is very tentative.
So it's an immigration problem?
Many cases are clearly linked to organised crime exploiting the ability to move people in a globalised economy - and the government knows that as people become more mobile the threat of forced labour increases.
But the existence of British victims in Bedfordshire shows that it is not exclusively an immigration problem.
How can slavery exist in a modern society?
Campaigners say that when you drill down into the definition of modern-day slavery, what we are fundamentally talking about is different forms of exploitation for commercial gain and often involving organised crime gangs.
Sometimes a gang completely controls a victim - but on other occasions they pass them on and take a profit.
Exploitation requires control, says Paul Donohoe of Anti-Slavery International.
Sometimes control is physical - such as a threat if someone tried to escape. Other times, an illegal immigrant victim is scared they will be reported to the police by the very gang who are controlling them.
Complex international operations moving people across continents. A family in south-east Asia could pay up to £40,000 to get a family member into Western Europe, believing that they will be able to send back riches.
But that individual will often find themselves paying back a vast debt to the gang - with threats against the family back home if they do not comply.