JPMorgan Chase is suing the executive responsible for supervising Bruno Iskil, also known as the London Whale, reports Bloomberg.

The bank lost at least $5.8 billion this year due to market-moving derivatives trades made by Iskil.

“Javier Martin-Artajo, Iksil’s boss in the chief investment office, is a defendant in a London lawsuit filed Oct. 22 by the bank,” says Bloomberg.

Both Iskil and Martin-Artajo are no longer with the bank. The New York Times reported earlier this year that Iskil has returned to his native France.

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