Complex sentence: The Portland Handicap is a flat horse race in the United Kingdom for three-year-old and above thoroughbreds run over a distance of 5 furlongs 140 yards (1,134 metres) at Doncaster Racecourse during the St. Leger meeting in September.
Split into simpler sentences: The Portland Handicap is a flat horse race in the United Kingdom for three-year-old and above thoroughbreds. It is run over a distance of 5 furlongs 140 yards (1,134 metres) at Doncaster Racecourse during the St. Leger meeting in September.