Britain Flash Crash

British financial trader Navinder Singh Sarao, who is fighting extradition to the U.S. where he faces charges of using lightning-fast software to manipulate futures contracts, is shown in courtroom sketch. (Elizabeth Cook/PA/Associated Press)

A British financial trader accused of helping to set off a "flash crash" on Wall Street in 2010 from his London home claimed Wednesday he was just good at his job as he fights extradition to the U.S.

U.S. authorities have accused Navinder Singh Sarao, 36, of contributing to the dramatic falls seen five years ago to the day through his use of lightning-fast software. They claim Sarao used a bluffing technique that allowed him to make nearly $880,000 US on the day that the Dow Jones industrial average plunged 600 points in less than seven minutes.

Sarao appeared at a London court Wednesday, where he failed in a bid to have the payment of a £5 million ($9.1 million Cdn) security payment removed from his bail conditions. The sum is equivalent to what his legal team said he has in his trading account. His parents also have to provide a security of £50,000 ($91,500).

Lawyer James Lewis, defending Sarao, told the hearing that it was impossible to supply the security because the trader's assets have been frozen. But Judge Elizabeth Roscoe ruled that the bail conditions should not be changed.

As he was being led away from the dock Sarao turned to the public gallery and said: "I haven't done anything wrong apart from being good at my job. How is this allowed to go on, man?"

Sarao, a former bank employee, is charged with fraud, commodities manipulation and other offences. He was arrested in London in April. U.S. authorities claim Sarao and his company, Nav Sarao Futures Limited, made £26 million over five years.

Securities investigators in the U.S. allege he used lightning-fast software to manipulate the market for E-Mini S&P 500 futures contracts on the Chicago Mercantile Exchange.

Sarao allegedly employed a ruse called spoofing, a bluffing technique in which traders try to manipulate the price of stocks or other assets by making fake trades to create the impression they want to sell when they really want to buy, or vice versa.