- Detective Chief Inspector Phil Brewer is head of the Met's Anti-Slavery Unit
- By the end of June, police have had 820 reports of slavery reported to them
- DCI Brewer said it was up to the industries involved to report suspicious activity
- New legislation passed in 2015 imposed life sentences for slave gang leaders
Detective Chief Inspector Phil Brewer, head of Scotland Yard's anti-slavery unit, has revealed a surge in cases in the capital in 2017 where people are working against their will, for no pay and in dangerous conditions.
In the year to the end of June police have had 820 cases referred to them - compared to 1,013 in the whole of 2016.
Servants kept prisoner in poorer communities or in ethnic minorities also needs to be stamped out because some group think it is culturally acceptable.
Detective Inspector Brewer told Reuters: ' Everyone realises now we're never going to police our way out of this.
'Labour exploitation in London is really misunderstood or not understood, it's quite clear that it's about what we don't know rather than what we know'.
The growth in cases is partly due to increased awareness about slavery, and as police and local authorities are now more often considering whether those involved in potential slavery crimes are victims rather than suspects.
Government departments, local authorities and police are investigating whether people in the construction and hospitality industries are being forced to work against their will.
There are an estimated 13,000 victims of forced labour, sexual exploitation and domestic servitude in Britain, according to Government data.
As paperwork is often only processed through embassies, police only hear about mistreatment if domestic workers come into contacts with officers for other reasons, Detective Inspector Phil Brewer said.
Domestic servitude is also fuelled by cultural factors that might make it acceptable in some sections of London's population to have a worker from a lower social group working as a domestic slave even though it is against the law.
The police had faced criticism because officers had treated potential victims as suspects, so London's police now 'massively relies' on relationships with charities and advocacy organisations to ensure swift support for victims.
Under the 'county lines' crime model, for example, young urban gang members are compelled and threatened to deal drugs in more rural areas.
Some of these young people are now being referred as victims, a number that Brewer expects to grow.
Police also needed to have much more 'grown-up conversations' with companies that find modern slavery in their supply chains, to calm their fears that reporting cases would result in them being prosecuted.
'There's not really been any conversation about how companies can actually interact with policing. There's probably some reassurance that we need to do, that if you come to us and say we found this, it won't compromise your position,' Detective Inspector Brewer said.