Financier Jho Low, who investigators believe is at the centre of one of the largest-ever financial scandals, kept up a stream of messages to an official at AmBank. Low was obsessed about how the bank handled the peculiar accounts of Malaysian Prime Minister Najib Razak.

Don't let people outside the bank or more than a few people inside know about the accounts, he instructed. Use Gmail, not the bank's email system, for communication. Whatever you do, don't send credit card statements to the prime minister's house.