Complex sentence: Jack Riley was an English professional rugby league footballer of the 1900s, playing at representative level for England, and at club level for Halifax, as a, i.e. number 8 or 10, during the era of contested scrums.
Split into simpler sentences: Jack Riley was an English professional rugby league footballer of the 1900s, who played at representative level for England, and at club level for Halifax. He played as a, i.e. number 8 or 10, during the era of contested scrums.