The BBC describes one fraud built on top of another:
Mercuria, one of the five-biggest oil traders in the world, is seeking redress in Turkish and UK courts against the copper supplier Bietsan Bakir.
In cases of non-delivery a trader could make a claim against a cargo's insurance policy. But Mercuria found that just one out of seven contracts used by the Turkish company to insure the cargo was real. The rest had been forged.