In April and May 2012, large trading losses occurred at JPMorgan's Chief Investment Office, based on transactions booked through its London branch. The unit was run by Chief Investment Officer Ina Drew, who later stepped down. A series of derivative transactions involving credit default swaps (CDS) were entered, reportedly as part of the bank's "hedging" strategy. Trader Bruno Iksil, nicknamed the London Whale, accumulated outsized CDS positions in the market. An estimated trading loss of $2 billion was announced. However, the loss amounted to more than $6 billion for JP Morgan Chase.