Author William Cohan, former managing director of JP Morgan Chase, says some of the emails that have been found are "quite damning".

BBC: US rules 'clear' on Iran business

The incident raises questions about his future, according to William Cohan, author of House of Cards: A Tale of Hubris and Wretched Excess on Wall Street.

BBC: Sign outside JPMorgan offices

The paradoxical message of William Cohan's compelling history of the world's most envied and recently at least most pilloried securities firm is that much of what Goldman does seems to warrant admiration and opprobrium in equal measure.

ECONOMIST: The firm that came to dominate world finance