Complex sentence: Their son James Gillespie who was instrumental in establishing the Mulligans Flat Public School and a regularly contributor to the Goulburn Evening Penny Post under the pseudonym "The Wizard".
Split into simpler sentences: Their son James Gillespie was instrumental in establishing the Mulligans Flat Public School. Gillespie was also a regularly contributor to the Goulburn Evening Penny Post under the pseudonym "The Wizard".