Thailand’s slave-labour surge has been driven by collapsing fish stocks and voracious demand for cheap seafood from Western consumers. Vessels are staying out longer, going further for diminishing returns and using human-trafficking networks to boost incomes and crew ships cheaply.

Immigrants become prisoners on these boats, forced to work for little or no money for years at a time. Violence is rife. ‘One of my co-workers fell in the sea,’ describes one victim. ‘We were ordered to continue to work and prevented from helping him. He drowned.’