A British financial trader made hundreds of thousands of pounds on the day of a multi-billion dollar US stock market crash, a court heard.

Navinder Singh Sarao, 37, is fighting extradition to the US where he is accused of helping trigger the 2010 Wall Street "Flash Crash" from his parent's home 3,500 miles away in Hounslow, west London.

He faces 22 charges including wire fraud, commodities fraud, market manipulation, and "spoofing" - a practice of bidding or offering with the intent to cancel the bid or offer before execution - which carry sentences totalling a maximum of 380 years.

At an extradition hearing at Westminster Magistrates' Court in London, Mark Summers QC, representing the US government, said Sarao manipulated the market by making "false" and "fictitious" orders on the Chicago Mercantile Exchange (CME).

The futures trader made 875,000 US dollars on the day of the Flash Crash on May 6 2010, which saw the Dow Jones Industrial Average plunge 600 points in five minutes, wiping tens of billions of pounds off the value of US shares, the court heard.

He also earned four million US dollars through his trades on August 4 2011 and, in total, made 40 million US dollars (£26 million) illegally over five years, Mr Summers told the court.

"The prosecution allegation is that trade he engaged in is what is known as spoofing," he said.

"Spoofing is market manipulation. The Government allege he spoofed the market.

"It is dishonest trading.

"He never had the intention of seeing these fictitious and false orders being executed.

"They were not real orders. They were there solely to manipulate the market price."

Sarao is accused of placing multiple orders before cancelling them without executing them, causing prices to fall.

US prosecutors claim that when the prices fell, Sarao then sold futures contracts, only to buy them back at a lower price.

Conversely, when the market moved back up as the activity ceased, Sarao allegedly bought contracts, only to sell them at a higher price, the US Justice Department said.

Mr Summers said that over the course of four years Sarao used his own software to modify his orders 7.4 million times to prevent them being executed - accounting for 42% of all modifications across the entire market.

Wearing a dark grey suit, dark shirt and light blue tie, Sarao - who has Asperger's syndrome - sat with his head bowed throughout the hearing.