Complex sentence: After leaving school he worked in a bingo hall and as a stableboy where after working there for three days he asked if he could try and ride a horse, the trainer agreed and the first horse he ever rode was Red Rum.
Split into simpler sentences: After leaving school he worked in a bingo hall and as a stableboy. After working there for three days he asked if he could try and ride a horse; the trainer agreed and the first horse he ever rode was Red Rum.