Final answer:
The Magna Carta initiated the democratic development in England by establishing the principle of limited government and legal rights such as due process, influencing later constitutional documents.
Step-by-step explanation:
The key event or document that initiated the process of democratic development in England is the Magna Carta of 1215. This pivotal document established the principle that even the monarch was subject to the law, laying the groundwork for constitutional government.
It included protections such as due process and the concept that a free man could not be penalized unless his peers had made a lawful judgment, principles that influenced many later documents, including the U.S. Constitution. While other documents and events, such as the English Bill of Rights (1688), the Glorious Revolution.