Bruno Iksil, the former JPMorgan Chase & Co. trader who became known as the “London Whale” as his unit began generating more than $6.2 billion in losses in 2012, surfaced on Monday to say he isn’t responsible for the debacle.

The Frenchman, who isn’t among former colleagues being prosecuted and has agreed to assist U.S. authorities in their cases, wrote in a letter sent to Bloomberg that he was “instructed repeatedly” by managers in the chief investment office, or CIO, to execute the strategy that went awry. He said he objects to the whale nickname and his association with the scandal.

“Publicity surrounding the losses sustained by the CIO of JPMorgan typically refers to ‘the London Whale’ in terms that imply that one person was responsible for the trades at issue,” he wrote. “In fact the losses suffered by the CIO were not the actions of one person acting in an unauthorized manner. My role was to execute a trading strategy that had been initiated, approved, mandated and monitored by the CIO’s senior management.”

Iksil’s 3 1/2-page letter breaks his longstanding public silence following the episode, which culminated in government probes, more than $900 million in regulatory sanctions against the bank and a 50 percent pay cut for Chief Executive Officer Jamie Dimon for one year. The U.S. Senate’s Permanent Subcommittee on Investigations and a task force formed by the New York-based bank separately released reports examining what happened, faulting lapses in areas including internal oversight and risk management.

Strategy Change

Iksil left the bank in 2012 and reached an agreement with the U.S. the following year, promising to testify against a more senior executive and a junior trader for allegedly hiding the extent of the losses. Neither of the defendants has come to the U.S. to face the charges. In his letter, Iksil said the government’s decision not to prosecute him helps show he’s not to blame. In July, the U.K. Financial Conduct Authority abandoned a proposal to fine Iksil 1 million pounds ($1.4 million) and refrained from banning him from the industry.

Iksil’s attorneys, Jonathan New and Jonathan Barr, confirmed the authenticity of his letter. Jim Margolin, a spokesman for Manhattan U.S. Attorney Preet Bharara, declined to comment on it, as did JPMorgan spokesman Brian Marchiony.

The trades in question were on tranches of credit-swap indexes. Tranches allow investors to wager on varying degrees of risk among a pool of companies. Credit swaps pay the buyer face value if a borrower fails to meet its obligations, less the value of the defaulted debt.

Iksil, who joined the CIO in 2005, became the chief trader for the credit-derivatives book in 2007. He used his portfolio to hedge against corporate-bond defaults as the U.S. economy weakened, and it produced a profit of about $2.5 billion during the five years ended in 2011.

Warnings Cited

In his letter, Iksil says he repeatedly warned superiors in 2011 and early 2012 about the potential for a large loss as they pressed him to carry out a revised trading strategy, part of an effort to reduce the unit’s risk-weighted assets, or RWAs. In September of 2011, he traveled to New York to meet with officials. “I described the very difficult market conditions, the elevated execution costs and lack of proper relevant information on the RWA figures,” he wrote. Still, managers kept pushing him to continue, he said.

When media reports appeared in April 2012 describing the bank’s growing positions, Iksil says he was singled out “for no good reason.” Because of the size of the bank’s bets, some market participants had already taken to calling him the London Whale.

“Still in 2016 ‘Bruno Iksil’ is associated with the moniker the ‘London Whale’ even though it was not a nickname I claimed for myself nor was I responsible for the losses resulting from a trading strategy directed by the JPM CIO’s management,” he wrote. “I have always acted in good faith both in the markets and for my employer.”