Final answer:
Access to coal, political and cultural factors, and a society rich in capital were the most important factors for the industrial revolution starting in Britain.
Step-by-step explanation:
The single most important factor that led to the industrial revolution starting in Britain was a combination of access to coal, political and cultural factors, and a society rich in capital.
Britain's proximity to coal mines allowed for easy access to this important energy source. Additionally, Britain had a parliament that supported the principles of free trade, which meant that commercial enterprises were not hindered by restrictions or prejudice.
The availability of capital through reliable banking institutions also played a crucial role in the industrial expansion.