In 2012, the global markets were rocked by revelations about a scam so massive it was almost hard to comprehend: the LIBOR ( London Interbank Offered Rate) scandal. Like the U.S. federal funds rate, LIBOR is a key benchmark short-term interest rate upon which other financial instruments are based. While the target for the U.S. rate is set by the Fed, LIBOR is the average of self-reported interest rates major banks charge one another to borrow money. By colluding to manipulate LIBOR, the banks’ traders raked in a fortune by betting on assets influenced by the interest rate. David Enrich followed the story while he was working for The Wall Street Journal and got close to the central figure in the scandal — star derivatives trader Tom Hayes.…