Britain's financial watchdog dropped Friday a probe into Frenchman Bruno Iksil, an ex JPMorgan trader known as the "London Whale" for massive gambles that led to losses of $6.2 billion (5.6 billion euros).
"We can confirm that we will not be taking any further action," said a spokeswoman for the Financial Conduct Authority, without giving further details.
Iksil's lawyer Michael Potts from law firm Byrne and Partners added: "I can confirm that the FCA has dropped its investigation into my client".
Potts said that the decision came after the FCA's Regulatory Decisions Committee, an independent panel of independent experts, had "rejected their case".
Derivatives trader Iksil had been under investigation in Britain for three years. A separate US investigation has also been dropped in exchange for his co-operation.
Spaniard Javier Martin-Artajo, Iksil's former boss, and Frenchman Julien Grout, a junior trader, are both being prosecuted in the same case, however.
The two allegedly kept false records on trades, committed wire fraud and submitted false US securities filings when they worked for the bank in London.
The US charges carry a maximum sentence of 65 years in prison and a fine of at least $5 million.
JPMorgan paid a fine of about $1 billion for poor oversight related to the trading loss.