Complex sentence: Harrington was the inventor of the papier-mâché goal posts and was President of the County Polo Association and the first President of the Polo Pony Society and was responsible for the establishment of the Polo Pony Stud book.
Split into simpler sentences: Harrington was the inventor of the papier-mâché goal posts and was President of the County Polo Association and the first President of the Polo Pony Society. He was responsible for the establishment of the Polo Pony Stud book.