Duke William of Normandy defeated and killed King Harold of England at Hastings on October 14, 1066, and by Christmas he was king. The two armies met on Senlac Hill, about seven miles from the coast, each carrying roughly 7,000 men. Harold had marched south at speed after beating a Norwegian invasion in the north. He lost. William won, and the whole of England changed hands in a single day.
Harold's men stood on the ridge behind a wall of shields. The position held for hours. The Norman cavalry charged up the slope and was beaten back, and the story that survives, told on the Bayeux embroidery, is that William's men broke twice and had to be rallied, once on a rumour that William himself was dead. He lifted his helmet to show his face. The battle turned on a feint, a pretended flight that pulled the English down off the hill, and on Harold's death near the end of the day.
How Harold died is argued. The embroidery shows a man struck in the eye by an arrow and another cut down with a sword, and the two figures may both be Harold, killed by an arrow and finished on the ground. What is certain is that the English line broke when he fell. William burned and marched through the south-east, and London surrendered rather than fight again. He was crowned at Westminster on Christmas Day.
It was a conquest, not a battle won and left. The old English nobility was stripped of its land over the next years and replaced by Normans, the language of the court changed, and the castles that still stand in the south were built to hold the country down. England had been ruled by a Scandinavian-linked line for a century. After Hastings it was tied to France, and stayed so for four hundred years.