Larry Pillard is to leave his job as chief executive of Tate & Lyle to take over the executive chairmanship of Tetra Laval, the privately owned Swedish packaging group.
He will move at the end of the year, but will remain a non-executive director of Tate.
A search has begun for a replacement, with both internal and external candidates likely. Tate shares fell from 377p to 366p when the announcement was made, although traders attributed this to the generally weak market.
Pillard joined Tate in 1992, to run Staley, its US starch business.
David Lang, food analyst at Investec, said: "Mr Pillard improved the technical performance of the plant out of all recognition. He's a very hands on engineer, he likes to clamber into the machinery."
Since becoming chief executive in 1996, and especially following the retirement of Sir Neil Shaw as chairman in 1998, Pillard has supervised a change in direction of the group, selling poorly performing businesses and pursuing growth from added value products.
At the same time, he is credited with driving cost savings through economic-value-added programmes and sorting out the ownership of Amylum, its European starch operation. The company, which was once a byword for disappointing investors, is now regarded as being on track for recovery.