On What Might Have Taken Place In 1066 at the Battle of Hastings Had the Norsemen Under Harald the Third Not Invaded Britain First, Depleted the Anglo-Saxons at the Battle of Stamford Bridge, etc.

Well it certainly would have made William's task much more difficult and had the Norman been repelled the whole history of Europe would have been different. My suspicion is that William would have returned to Normandy, consolidated his control over Brittany and Flanders, and possibly looked eastward for conquest, all the while while fearing a possible invasion from Godwinson and England......but we'll never know, right?