Complex sentence: At the time of its demise in 1996 the Poly was Europe's oldest regular marathon, it had seen more world records than any other marathon and it had been run over 26.2 miles more often than any other marathon.
Split into simpler sentences: At the time of its demise in 1996, the Poly was Europe's oldest regular marathon. It had seen more world records and had been run over 26.2 miles more often than any other marathon.