Six financial brokers were "willing and enthusiastic" players in a conspiracy to fix the Libor benchmark interest rate, prosecutors said as their trial opened on Tuesday.
The men, known by nicknames including "Lord Libor" and "Big Nose", acted to "corrupt a process that should not have been corrupted", London's Southwark Crown Court heard.
They are charged with conspiracy to defraud by trying to manipulate the London Interbank Offered Rate (Libor) linked to the Japanese yen.
Many of the world's top banks have been hit by scandals over the rigging of Libor rates, which is estimated to underpin the interest rates in some $500 trillion of contracts globally, including mortgages and consumer loans.
The six are also accused of conspiring with Tom Hayes, a former Tokyo-based trader for UBS who later joined Citigroup, and others, to manipulate the Libor rate between 2006 and 2010.
The jury was told Hayes was convicted of conspiracy to defraud in August.
The defendants are Noel Cryan, 49, from Kent; Danny Wilkinson, 48, James Gilmour, 50 and Terry Farr, 44, from Essex; Colin Goodman, 53, from Surrey, and Darrell Read, 50, of New Zealand's capital Wellington.
They were employees at the firms ICAP, Tullett Prebon and RP Martin.
Prosecutor Mukul Chawla said the case concerned "the dishonest and wide-scale manipulation of bank rates for profit", with the defendants agreeing to "interfere and abuse a critical financial process".
He said they did so to help a trader at a bank to "cheat" those who traded with him.
"That cheating enabled the trader to make literally millions of pounds for the banks," said Chawla.
He told the jury the defendants were rewarded in "various ways".
"Each of these six defendants were brokers, middle men, willing and enthusiastic to lend themselves to Mr Hayes' dishonest scheme," Chawla told the court.
The six defendants deny all the charges.
The trial is set to last up to 14 weeks.