Complex sentence: When Abram Lyle & Sons merged with Henry Tate & Sons in 1921 to form Tate & Lyle, he became a director of the new company, then its chairman in 1928, and president in 1937.
Split into simpler sentences: When Abram Lyle & Sons merged with Henry Tate & Sons in 1921 to form Tate & Lyle. He became a director of the new company, then chairman in 1928, and president in 1937.