Hiscox Insurance Company managing director Sian Fisher has resigned her post, with effect from 7 February 2004.
Fisher, who has been with Hiscox for 18 years, is to begin an MBA at Harvard in April this year.
Hiscox chief executive Bronek Masojada will assume direct responsibility for Hiscox Insurance Company until a replacement has been appointed.
Fishes said: "This year is the 18th year that I will have worked at Hiscox and after this length of time I feel that I need to consider some new challenges outside Hiscox."
She joined Hiscox in 1986 as a Lloyd's underwriter and held a number of executive roles before becoming managing director of Hiscox Insurance Company in 2001.
A spokeswoman for Hiscox said the company had already begun to seek a replacement, but that there was no firm timescale for when an appointment would be made.
