Complex sentence: Resident trainers in the sixties included Frank Heald, Bill Savage and Wilf Flint as the stadium owned a significant number of the greyhounds that provided the graded racing strength, handicaps were also very popular.
Split into simpler sentences: Resident trainers in the 1960s included Frank Heald, Bill Savage and Wilf Flint. The stadium owned a significant number of the greyhounds that provided the graded racing strength, handicap races were also very popular.