Shares in motor insurer Admiral (LON:ADM) sank on Wednesday as it emerged Henry Engelhardt, chief executive since 1991, two years before it launched, is stepping down from the helm.
Chief Operating Officer David Stevens, 51 will replace him in a year's time.
Group chairman Alastair Lyons said: "There is no way to measure adequately the contribution of the founder of a business that has grown from zero to over £4 billion market capitalisation, employs over 7,000 people and serves more than 4 million customers.
"On behalf of the board and the entire group I want to thank Henry for everything he has done over so many years and will continue to do until he steps down in 12 months time. Equally, we are hugely fortunate to have someone of David's capability and experience to succeed Henry and I am very confident that Admiral will continue to go from strength to strength in the future."
Engelhard, 57, has seen the Cardiff- based company grow to become the UK's second largest motor insurer and has a personal 12% stake in the group.
In March last year, he colourfully compared the firm's 2013 year and results to a "baked potato".
"It was a good, solid year, something on the plate that is appreciated but doesn't really grab the spotlight," he said.
Meanwhile, profits stalled in 2014 due to a tough year for premiums and its comparison website arms.
Today, Engelhard said: "Don't bury me yet, Guys! I still have 12 months on the job and lots to accomplish in that time. But I see the wealth of management talent we have rising up in the organisation and I think that in a year it will be the right moment to start the transition towards that younger, very talented team."
Admiral shares today eased 1.15% to 1,458p.