Edit: also make note that approximately one thousand years ago englishmen and norwegians understood each other perfectly, the languages were quite similar. As a reference, Iceland has held their language pure, take a look at youtube to hear how it most likely sounded like.

Eh, not quite. Old English and Old Norse were already pretty different by then. The split between West and North Germanic languages happened a long time ago. They would not have been able to communicate more than simple phrases in their native languages. Also Icelandic, though very archaic in most respects, has undergone lots of changes in pronunciation since then and probably sounds very different from Old Norse.