The trader at the centre of the so-called "London whale" trading debacle - which cost US$6 billion in losses - broke nearly four years of silence by sending a three page letter to a range of financial publications, taking aim at former employer JP Morgan Chase & Co, reports the Wall Street Journal. Bruno Iksil alleged the losses suffered by the CIO were not the actions of one person acting in an unauthorized manner. Iksil writes in his letter: "My role was to execute a trading strategy that had been initiated, approved, mandated and monitored by the CIO's senior management."