Standard Chartered bank has denied allegations from US regulators that it illegally "schemed" with Iran to launder as much as $250bn (£161bn) for nearly a decade.
The bank faces claims that it hid 60,000 secret transactions for "Iranian financial institutions" that were subject to US economic sanctions, and has been threatened with having its US banking licence revoked.
Author William Cohan, former managing director of JP Morgan Chase, says some of the emails that have been found are "quite damning".
"I think the rules in the United States are pretty clear about doing business with the Iranians at this point," he said.
David Green, former head of international policy for the Financial Services Authority, says the fact that dollar denominated transactions ultimately have to be settled in New York potentially gives the US authority to get a handle on a large proportion of transactions in the world.
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