Complex sentence: The Fillies' Mile is a Group 1 flat horse race in the United Kingdom for two-year-old thoroughbred fillies run over a distance of 1 mile at Ascot Racecourse in late September.
Split into simpler sentences: The Fillies' Mile is a Group 1 flat horse race in the United Kingdom for two-year-old thoroughbred fillies. It is run over a distance of 1 mile at Ascot Racecourse in late September.