The crucial event in 1066 that changed the course of British history was the Norman Conquest, marked by the Battle of Hastings. William the Conqueror, Duke of Normandy, invaded England and defeated King Harold II. This victory led to the establishment of Norman rule in England and significant shifts in the country’s societal structure, governance, and culture. The Normans introduced feudalism, reshaped land ownership, and enriched English architecture and language. The conquest also facilitated the integration of Norman and Anglo-Saxon cultures, thereby setting the foundations for modern England.