Britain won, on average, 17 gold medals per Olympics in the five official games held in its imperial heyday before World War I. That average has dropped to only five medals per Olympics in the 17 held since.
Britain is one of the best countries in the Olympics. 
mnli hypothesis: Britain is one of the best countries in the Olympics.  premise: Britain won, on average, 17 gold medals per Olympics in the five official games held in its imperial heyday before World War I. That average has dropped to only five medals per Olympics in the 17 held since.