All you need to know about Bill Hwang and his $20 billion Historic Margin Call.

Bill Hwang, whose family business, Archegos Capital has been widely reported to be behind $20 billion of share sales that shook Wall Street on Friday, is at once a fearless investor, an acknowledged insider trader, and a committed Christian.

The $20 billion drama started with a series of giant block trades handled by Goldman Sachs and Morgan Stanley in companies including GSX Techedu, Baidu, Vipshop Holdings, Farfetch and Tencent Music Entertainment. But it was the sales of big chunks of stock in well-known US media groups ViacomCBS and Discovery that really shook Wall Street.

The sales sparked a series of frantic questions like Who was selling? Why were they selling? And how much more selling might occur? and Over the weekend all fingers started pointing to Archegos and Hwang.

The Financial Times reported that falls in Viacom between Tuesday and Thursday caused an almighty margin call from one of the fund’s prime brokers. Other banks got nervous and before much comprehension, $20 billion of stock had been dumped.

Now, Hwang is MIA and Archegos Capital has taken down its website. But it didn’t take long until his controversial past was being investigated and discussed in detail.

Down to a brief background of the “Tiger Cub,” Hwang. Hwang worked at Tiger Management, the hedge fund run by Wall Street titan Julian Robertson, before running a fund called Tiger Asia. He remitted cash to investors in 2012 after being accused of insider trading in Chinese bank stocks and admitting wire fraud. He paid $44 million to settle illegal trading charges brought against him by America’s Securities and Exchange Commission over the incident and this also led to his 2014 ban from trading in Hong Kong.

On Sunday, there have been suggestions Hwang might have been involved in trying to orchestrate a short squeeze in GSX by John Hempton (an Australian short seller), a Chinese education group that has become a battleground stock for bulls and short sellers, which saw its stock surge 175 per cent between January 1 and January 27.

Viacom and Discovery were also heavily shorted stocks that had surged before last week’s ugly falls, apparently thanks to short squeezes. Viacom, for example, rose 258 per cent between the start of October and the start of last week. Discovery was up 259 per cent over the same period.

But with the Viacom’s wobbles last week came a margin call hit on Hwang. Thus, whatever gains Hwang might have enjoyed in Viacom and Discovery must have been limited by his use of leverage.

As with the GameStop episode earlier this year, the fall of Archegos will cause some big dramas for individual stocks, but its impact on the broader market should be limited.

But as with the damage the GameStop short squeeze did to hedge funds that had big short positions, the Archegos sell-off serves as a reminder to investors of how debt can amplify gains or losses in ways markets struggle to predict.

Clearly it’s surprising that a relatively unknown investor, Hwang, could have enough leverage to necessitate a $U20 billion margin call. But given what we’ve already seen in 2021, it’s hard to be truly shocked.