Navinder Singh Sarao
Navinder Singh Sarao at Westminster magistrates\' court Twitter

Navinder Singh Sarao, the trader who allegedly caused the Wall Street Flash Crash, has made more than $40m (£26.3m) by rigging stock markets, a court in the US heard. The West Londoner, who manipulated markets from his house in Hounslow, lost companies tens of billions of dollars, it is alleged. Sarao had attempted to postpone extradition to the US after he was freed on bail from a London prison, but had failed.

His indictment in the US started on 3 September as evidence was presented in front of a federal grand jury in Chicago. Jurors heard that Sarao has allegedly spoofed US markets for years, meaning that he set up a large order for certain shares, and then cancelled the order, temporarily hiking up those share prices. With the knowledge of when share prices would rise, he could manipulate the markets.

Evidence also suggested that Sarao had been seeking advice from fellow traders about spoofing as early as 2009, while it was formerly thought that he did not start the market fixing until June that year.

The indictment also showed evidence of Sarao making extensive attempts to get to grips with the system and exploiting it optimally. An email, in which the trader spoke of a tactical approach where he kept changing the sizes of orders, or clips, read: "If I keep entering the same clip sizes, people will become aware of what I am doing, rendering my spoofing pointless."

On 14 August, Sarao was released on bail from Hounslow prison. The trader told Westminster magistrates' court at an earlier hearing that he could not access the money needed to pay out the £5.05m bail requirement because of long-term investments. He would not be able to access the money until 2017, he said.

Sarao, who had been in custody since 22 April, was charged by US regulators with market manipulation and wire fraud as well as commodities fraud. The judge forced Sarao to reveal where he had hidden his money, and the west Londoner told the court he has £25.5m (€55.9m, $39.8m) locked away in Swiss bank accounts.