viking stronk

What if the Vikings had managed to conquer Paris sometime around the 9th century? How much more territory would they be able to overrun, besides Ile-de-France? What would happen to the title of the King of West Francia? Would it go extinct? What would happen to his vassals, would they splinter...

So, suppose that kings Alfred and Aethelred of Wessex are much less lucky in beating back the Great Heathen Army, and see their lands conquered by it instead. England becomes "Jorvik", a brand new Norse state, or collection of warlord states, in the late 9th century. So, what are the effects on...