Achilles Macris, who was based in London, would have been hit with a £1,132,747, penalty had a settlement not been agreed.

In the role he was responsible for a number of portfolios, including the Synthetic Credit Portfolio, at the time of what became known as the ‘London Whale’ trades, officials explained.

Mr Macris was the main contact with the FCA’s predecessor the Financial Services Authority in relation to CIO International and as an approved person he was required to deal with the Authority in an open and cooperative way, the FCA said.

Mr Macris did not inform the authority about concerns with the Synthetic Credit Portfolio between 28 March 2012 and 29 April 2012, the FCA stated, saying that as a result he failed to meet the standards expected of an approved person under Statement of Principle 4.

Mark Steward, director of enforcement and market oversight said: “A failure to communicate openly with us can affect the well-running of markets and cause unnecessary harm to investors, especially in times of financial stress or crisis.

“Regulators need open communication with firms so that better decisions can be made sooner. Mr Macris should have explained the position more squarely especially when he knew the Synthetic Credit Portfolio’s losses had worsened.”

An FCA statement read: “The Synthetic Credit Portfolio began to suffer significant losses from the beginning of 2012. On 23 March 2012 the front office was instructed that no further trades should be executed on the portfolio until discussions had taken place.

“Mr Macris subsequently asked that daily risk reports for the Synthetic Credit Portfolio be produced and in the following days took other measures, such as requesting assistance from outside CIO and arranging daily progress meetings with CIO Risk and the front office. Despite these measures the Synthetic Credit Portfolio continued to suffer losses.”

The FCA said he had failed to inform them of the full extent of the difficulties that the Synthetic Credit Portfolio was then facing or to take steps to ensure that the Authority understood there were causes for concern with the portfolio.