Hemery's first International title came at the 1966 Commonwealth Games, where he won the 120 yd hurdles in 14.1 seconds, a title he retained four years later at the 1970 Commonwealth Games (by then it was the 110m hurdles which he won in 13.8 seconds).
In 1969, Hemery won a silver at the European Championships in the 110m hurdles, but missed the next European Championships in 1971 due to injury.