Gary Stevenson, the author of “The Trading Game,” spent his early 20s trading trillions of dollars for Citibank in London and Tokyo.

He claimed to have won the job playing a card game and eventually became Citibank’s most profitable trader. While some of his colleagues lived a life fueled by partying and cocaine, Gary earned millions betting against the global economy. He talks to Business Insider about office culture in Canary Wharf, London, the bosses, and the bonuses. He covers the mindset of profitable bankers, their daily routine, and what leaving the job is like.

Now, Gary is a published author and teaches economics through his YouTube channel Garyseconomics.