(June 24): Markus Braun started last week with a US$1 billion (S$1.39 billion) stake in Wirecard AG, the digital payments company he ran. By the end of the week he was out of his job as chief executive officer and more than half his shares had been liquidated to meet a margin call.

Braun, who surrendered to police in Munich late Monday as part of a probe into the firm’s accounting practices, disposed of 5.5 million shares on Thursday and Friday, according to regulatory filings, confirming an earlier Bloomberg News report. That leaves him with a 3% stake valued at roughly US$60 million.

Authorities are investigating how 1.9 billion euros (S$2.99 billion) went missing from the company, a scandal that has triggered calls for regulatory reform.

Braun, 51, pledged about half of his stake in December 2017 to secure a 150 million-euro credit line. That loan was provided by Deutsche Bank AG, which has since divested it, according to people familiar with the matter.

On Wednesday, those pledged shares were worth 435 million euros, easily covering the value of the loan. But after Wirecard disclosed that it was unable to locate 1.9 billion euros, or about a quarter of its balance sheet, their value collapsed to 166 million euros on Thursday, triggering the sales. By Friday, they were worth about 100 million euros.

Share pledges are an increasingly popular mechanism among executives and wealthy investors to unlock cash without giving up control of their holdings. Banks have sought to increase lending to their wealthiest -- and most profitable -- clients in recent years. Secured lending against company stock is a way to deepen a relationship and bring in other business, such as lucrative fees for advice on mergers or stock listings.

But they can be risky for both parties. A soured margin loan to Lu Zhengyao, the billionaire founder of Luckin Coffee Inc., saw his fortune wiped out and contributed to an increase in first-quarter loan-loss provisions at Credit Suisse Group AG.