What do we know about Flash Crash trader Navinder Singh Sarao?

Who has been arrested?

Navinder Singh Sarao, a 36-year-old trader from Hounslow. He was born and raised in the UK.

The US Department of Justice has charged him with wire fraud, commodities fraud, commodities manipulation and 'spoofing', which carry prison sentences of between 10 and 25 years per count, or a possible $1m fine. The charges stem from the stock market Flash Crash in 2010 that wiped hundreds of billions of dollars off companies.

Family

Sarao is the youngest of three sons. Raj, the oldest, lives with his wife and two children opposite his parents' home, where Sarao allegedly worked as a day trader.

Neighbours said the family have lived in the quiet suburban street in Hounslow for many years.

Mahmood Atif, 36, who lives down the road from Sarao's parents, said: "They are a nice family. The family will be upset. It's a shock."

Education

Sarao is a graduate of Brunel University in West London.

A former school friend, who asked not to be named, told The Telegraph: "Navinder was really bright and was in the top set for all his subjects. He was a bit of a cheeky chap but was popular. He was a bit of a geek but was funny also. He studied Maths and Science at A Level. He was a bit of a prankster but never got caught."

In his school yearbook, his teacher wrote that he was late almost every day.

Anil Puri, 41, who works in web design, grew up round the corner from Sarao and went to primary school with him and his brothers.

He said: "We used to play football, badminton and athletics in the street when we were young. There were no computers in those days.

"He [Navinder] was very bright, a loud, chirpy chap, a friendly guy. He was the youngest of the three but he was the most confident. His nickname was Brooks but I can't remember where that came from.

"He was definitely an ambitious guy, definitely clued up, street wise."

Brinder Bedi, 39, another schoolfriend, said: "They were very close, all the boys. They all used to wear their football gear. Nav was sporty, he seemed to be a normal kid."

Career

He worked in banking before becoming a day trader, operating a business - Nav Sarao Futures - from his bedroom in his parents' semi-detached home in Hounslow, under Heathrow Airport's flight path.

Accounts for the year to October 2013 - the most recently available at Companies House - show cash on the balance sheet of £7.5m.

But prosecutors allege Sarao generated $40m (26.7m) of trading profits over a five-year period.

Filings at Companies House show as recently as last August he set up a second company, NavCorp Capital Markets, of which he was the only director.

Accounts for that company have not been filed, however.

He apologised to the Chicago Mercantile Exchange and his broker in March 2010 after placing and then cancelling a large number of orders. He said the reason for cancellation was because he had been showing a friend what was done “by the high-frequency [trading] geeks”.

A month before the flash crash, in April 2010, Sarao set up a corporate entity on the Caribbean island of Nevis, the criminal complaint claimed, called Nav Sarao Milking Markets.

In 2014, he told the Financial Conduct Authority he was successful at trading because “he had always been good with reflexes and doing things quick”.

After another effort to contact him in May 2010, Sarao is alleged to have emailed his broker to say that he had “just called” the Chicago exchange “and told ’em to kiss my a**”.

^{The DoJ's complaint against Sarao}