Spread-betting firm IG Group Holdings (LON:IGG) said its chief executive was retiring as it revealed a profit hit from the removal of the Swiss franc's peg to the euro.
IG said Tim Howkins, who also served as finance chief during 16 years at IG, would step down at IG's annual meeting in October.
After the meeting, chief operating officer Peter Hetherington will become interim chief executive, subject to regulatory approval.
IG said underlying pre-tax profits in the year to May 31 fell 0.9% to £193.2mln while reported pre-tax profit dropped 13%.
The group took a £27mln hit from the Swiss National Bank's shock decision in Janary to abandon the ceiling on the franc versus the euro.
The move sent the value of the franc soaring and created market turmoil, spelling disaster for some financial firms.
Chairman Andy Green said: "This was a salutary reminder, for both industry providers and existing clients, of the potential risks and rewards of trading in the financial markets.
"At IG we take very seriously our regulatory and consumer responsibilities on appropriateness tests for prospective clients.
"This incident underlines the need for regulators to ensure that regulatory standards are applied robustly and consistently across the industry."
He added: "IG clearly demonstrated its ability to manage through such a so-called 'Black Swan' event while maintaining a robust business. Following this, we have reviewed our robust risk management system and learned lessons."
Green said of Howkins's decision to retire: "Although I have only had the pleasure of working with Tim for the last year, I would like to express my personal gratitude. The board is disappointed to lose somebody with Tim's proven leadership skills but fully understands his decision."
During the year, IG launched an execution-only stockbroking product in the UK, Ireland and the Netherlands and extended it into Germany and Austria after the enxd of the year. It also acquired licences and opened offices in Switzerland and Dubai. It reported "active client growth across all regions".
Underlying revenue rose 8% to £400.2mln. The group kept its full year dividend at 28.15p, giving a final dividend of 19.7p.
Shares fell 50p to 757p in mid-morning London trading.