Excerpts from Books and Wikipedia
"In the most decisive battle ever fought on English soil, the mounted knights of William, duke of Normandy, famously defeated the army of King Harold II, which had hurried south from the Battle of Stamford Bridge on hearing of William's invasion. William claimed to have been promised the throne of England by King Edward the Confessor, but Harold, although he had sworn an oath to support William, had been crowned instead on Edward's death in January 1066. . . . He rewarded his followers with land, replacing the English nobility with Normans, Bretons, and Flemings. Norman law and feudalism were introduced, and Norman French became the language of the court. England would never be the same again." [1001 Days] Four claimants to throne after King Edward died in 1066: 1. Harold Godwinson, a relative of Edward's wife; powerful family and Edward may have acknowledged him on deathbed; 2. King of Denmark from descent thru Cnut, an earlier king of England; 3. King Harold Hadrada of Norway; 4. Wm of Normandy, supposedly promised throne by Edward the Confessor when Wm visited in 1052; [Aldrete Lectures: Decisive Battles]