In the early afternoon of 6 May 2010, panicked investors watched as the Dow Jones Industrial Average plunged 1,000 points in a matter of minutes. Although the index later recovered some of the losses, the few understood why this had happened.
It later emerged that the ensuing financial turmoil was due to a large trade executed in the United States. But regulators have now said Sarao's actions help explain why this massive trade was able to send markets into a tailspin.
Here are the three most surprising takes from the criminal complaint issued by regulators:
1. $40m (£27m)
That's the total amount Sarao is alleged to have made in the four years to 2014. That's about five times his bail, and enough to buy a stately home in the countryside, or a luxury flat in Hyde Park.
"Overall, between 2010 and 2014, Sarao made approximately $40 million trading E-Minis," the criminal complaint said.
2. "Kiss my ass"
Sarao apparently told his futures commission merchant (FCM) - or broker - he had told United States regulators to "kiss my ass". Nice.
"The CME (Chicago Mercantile Exchange) provided a copy of the latter correspondence to Sarao's FCM, which suggested to Sarao in an email that he call the FCM's compliance department if he had any questions. In a responsive email dated May 25, 2010, Sarao wrote to his FCM that he had "just called" the CME "and told em to kiss my ass," it said.
3. "Milking markets"
The US regulators say Sarao even created a fund which he not-so-subtly named "Milking Markets", registered in the Caribbean and allegedly used for tax avoidance purposes.
"In late April 2010, Sarao established a new entity, Nav Sarao Milking Markets Limited, which was incorporated in Nevis," it said.
Sarao appears to have created this company as part of a tax avoidance strategy pursuant to which he 23 also established, in 2012, International Guarantee Corporation, incorporated in Anguilla."