The strength of the Viking influence on Old English appears from the fact that the indispensable elements of the language - pronouns, modals, comparatives, pronominal adverbs (like "hence" and "together"), conjunctions and prepositions - show the most marked Danish influence; the best evidence of Scandinavian influence appears in the extensive word borrowings for, as Jespersen indicates, no texts exist in either Scandinavia or in Northern England from this time to give certain evidence of an influence on syntax. The change to Old English from Old Norse was substantive, pervasive, and of a democratic character. Old Norse and Old English resembled each other closely like cousins and with some words in common, they roughly understood each other; in time the inflections melted away and the analytic pattern emerged. It is most “important to recognize that in many words the English and Scandinavian language differed chiefly in their inflectional elements. The body of the word was so nearly the same in the two languages that only the endings would put obstacles in the way of mutual understanding. In the mixed population which existed in the Danelaw these endings must have led to much confusion, tending gradually to become obscured and finally lost.” This blending of peoples and languages happily resulted in “simplifying English grammar.”
What language was spoken in Northern England after the Viking invasions?
Old Norse