LONDON (AP) — 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 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 pound ($7.5 million) 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 pounds.

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 offenses. He was arrested in London in April. U.S. authorities claim Sarao and his company, Nav Sarao Futures Limited, made 26 million pounds over five years.