When firms say they have found no evidence of modern slavery, that should ring alarm bells.

Statistics on the scale of this issue are becoming as well known as they are shocking. Estimates put the number of modern slavery victims at almost 50 million globally – including those in forced labour or living in forced marriages. Of these, 17.3 million are being forced to work by private businesses, with nearly 4 million in forced labour imposed by state authorities. More than 3.3 million of those in forced labour are children.