The head of Scotland Yard’s anti-slavery police unit has warned that London is now a global hotspot for modern-day slavery with victims forced to work in the construction and hospitality industries.

“Everyone realises now we’re never going to police our way out of this,” Detective Chief Inspector Phil Brewer told Thomson Reuters, revealing that the capital has seen a surge in cases of slavery this year.

In 2017 to the end of June police have had 820 cases referred to them which concern people forced to work against their will without pay, and often in dangerous conditions — compared to 1,013 in the whole of last year.

The Metropolitan Police needs staff working in restaurants, hotels and in industries like construction to blow the whistle on slavery cases, and said that charities can also help with finding victims.

Speaking on the fight against domestic servitude in Britain’s capital, Brewer said the practice is being fuelled by cultural factors which mean it is seen as acceptable in some communities to keep someone from a lower social group prisoner, even though it’s against the law.

“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,” he said.

One of the biggest challenges for the Metropolitan police is to make sure every officer in the force of 30,000 understands and reacts appropriately to modern slavery cases, said Brewer.

Along with police, government departments and local authorities are investigating whether people in the construction and hospitality industries are being forced to work as modern-day slaves.

Prime Minister Theresa May promised to lead the fight against modern-day slavery, with Britain passing the Modern Day Slavery Act in 2015, which introduced life sentences for traffickers and forced companies to disclose their efforts to ensure their supply chains are free from slavery.

According to government data, there are an estimated 13,000 victims of forced labour, sexual exploitation and domestic servitude in the UK.

In October, a new report to Parliament said that there are “too many gaps” in the action being taken to protect victims.

Warning that Europe’s “migrant crisis” was being used by traffickers to lure people into servitude, Britain’s independent anti-slavery commissioner Kevin Hyland said that African women trafficked into prostitution, and men from Eastern Europe “exploited in shocking conditions in car washes” were among those being forced unlawfully into slavery.