Complex sentence: James Crossley was a professional rugby league footballer who played in the 1930s, and 1940s, playing at club level for Castleford, as a, i.e. number 11 or 12, during the era of contested scrums.
Split into simpler sentences: James Crossley was a professional rugby league footballer who played in the 1930s, and 1940s. He played at club level for Castleford, as a, i.e. number 11 or 12, during the era of contested scrums.