When and how did the English possessions originate in France?

On the territory of the British Isles in the early Middle Ages, there were a large number of states of the Angles, Saxons and Suevi. Also, there were settlements of Vikings (Normans), who regularly came with raids and partly remained here. All states constantly competed with each other.
In 1056, the islands were invaded by Norman troops led by William the Conqueror. His native lands were in the north of France. Having become the king of England and the ruler of most of the territories on the islands, Wilhelm also retained the former French possessions.