A British-based trader working for America's biggest bank is suspected by financial analysts of being involved in a £2bn loss at JPMorgan Chase after the investment group made massive and hugely risky trades when it should have been trying to mitigate risk.
No wonder, then at the banker's nickname: he is known as Voldemort, The London Whale, or simply the White Whale.
According to the Washington Post, the Whale's real name is Bruno Michel Iksil. He is said to be French-born and based in London, and worked for the Chief Investment Office (CIO) at the heart of the bank's recent losses.
In a shock conference call after trading closed on Thursday Jamie Dimon, the bank's chief executive, blamed the CIO and "many errors, sloppiness and bad judgement" for the losses and said that another $1bn could be lost by the end of the quarter.
Dimon did not name any specific executive or employee of JPMorgan, or identify exactly which trades had caused the losses, but said the CIO - designed to hedge the bank against risk - "proved to be riskier, more volatile and less effective as an economic hedge than we thought".
A photo has been leaked of what anonymous bloggers say is Iksil's Bloomberg profile, including references to personal humility, but it has not been possible to verify the claims.
Little else is known about Iksil - but the size of his portfolio tells its own story. In April, hedge funds and analysts reported via the Wall Street Journal that Iksil's bets were on such a scale that on their own they could move prices in markets worth trillions of dollars.
The financial news service Bloomberg claimed Iksil's group of traders had a portfolio worth at least $200bn, and that while the CIO generated $5bn in profits in 2010 it now appears to have taken those risks too far.
According to analysts, it was suggested that the CIO was not just attempting to mitigate risk but was instead taking huge risks to make profits for the bank.
While neither JPMorgan or Iksil were accused of wrongdoing, news reports alleged the bank's trading desk was engaged in speculative trading, and critics in the US have cited it as a reason for legislation to prevent government-insured banks taking big risks on the markets with their own money.
Indeed, in April Bloomberg reported that the 'Whale' was not the only trader at JPMorgan said to be taking massive risks that could endanger markets.
Another banker, Achilles Macris, who was hired in 2006 to run the CIO, was said to have bets "so large that JPMorgan probably can't unwind them without losing money or roiling financial markets", Bloomberg was told by former executives at the bank.
The implication that more traders could be involved will do nothing to sate the markets - especially since the bank was previously praised for its risk-averse conduct prior to the 2008 banking crisis.
The bank's shares lost 7% in value in after-hours trading, and also hit other banking stocks including Bank of America and Goldman Sachs.
"These were grievous mistakes, they were self-inflicted, we were accountable and we happened to violate our own standards and principles by how we operate the company," the bank's chief executive added.
"We will admit it, we will learn from it, and we will move on."
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