Complex sentence: Instead of phoning for an Ambulance, his then partner, Fiona Hartman, went to the bank to withdraw Jim's money, and put on an act when Julie and Rosemary discovered his body.
Split into simpler sentences: Instead of phoning for an ambulance, his then partner, Fiona Hartman, went to the bank to withdraw Jim's money. Pretending to be unaware of Jim's plight she later put on an act when Julie and Rosemary discovered his body.