Signs that modern slavery victims were being forced to work at a McDonald’s branch and a factory supplying bread products to major supermarkets were missed for years, the BBC has found.

A gang forced 16 victims to work at either the fast-food restaurant or the factory - which supplied Asda, Co-op, M&S, Sainsbury’s, Tesco and Waitrose.

Well-established signs of slavery, including paying the wages of four men into one bank account, were missed while the victims from the Czech Republic were exploited over more than four years.

McDonald’s UK said it had improved systems for spotting “potential risks”, while the British Retail Consortium said its members would learn from the case.

Six members of a family-run human trafficking network from the Czech Republic have been convicted in two criminal trials, which were delayed by the Covid pandemic.

Reporting restrictions have prevented coverage of much of the case, but BBC England can now reveal the full scale of the gang’s crimes - and the missed opportunities to stop them.

Nine victims were forced to work at the McDonald’s branch in Caxton, Cambridgeshire. Nine worked at the pitta bread company, with factories in Hoddesdon in Hertfordshire and Tottenham in north London, which made supermarket own-brand products. There were 16 victims in total across both sites, as two worked at both McDonald’s and the factory.

The victims - who were all vulnerable, most having experienced homelessness or addiction - earned at least the legal minimum wage, but nearly all of their pay was stolen by the gang.

While they lived on a few pounds a day in cramped accommodation - including a leaking shed and an unheated caravan - police discovered their work was funding luxury cars, gold jewellery and a property in the Czech Republic for the gang.

On several occasions, victims escaped and fled home only to be tracked down and trafficked back to the UK.

The exploitation ended in October 2019 after victims contacted police in the Czech Republic, who then tipped off their British counterparts.

But warning signs had been missed for at least four years, the BBC has discovered by reviewing legal documents from the gang’s trial and interviewing three victims.

The undetected red flags include:

• Victims’ wages were paid into bank accounts in other people’s names. At the McDonald’s, at least four victims’ wages - totalling £215,000 - were being paid into one account, controlled by the gang
• Victims were unable to speak English, and job applications were completed by a gang member, who was even able to sit-in on job interviews as a translator
• Victims worked extreme hours at the McDonald’s - up to 70 to 100 a week. One victim worked a 30-hour shift. The UN’s International Labour Organization says excessive overtime is an indicator of forced labour
• Multiple employees had the same registered address. Nine victims lived in the same terraced home in Enfield in north London while working at the bakery

“It really concerns me that so many red flags were missed, and that maybe the companies didn’t do enough to protect vulnerable workers,” said Dame Sara Thornton, the former independent anti-slavery commissioner, who reviewed the BBC’s findings.

Det Sgt Chris Acourt, who led the Cambridgeshire Police investigation, said there were “massive opportunities” that were missed to detect the slavery and alert authorities sooner.

“Ultimately, we could have been in a situation to end that exploitation much earlier had we been made aware,” he said.