language contact and historical analogies

I've just been reading Terry Hoad's chapter 'Before English' in The Oxford History of English. He compares the situation in the fifth and sixth centuries in Britain (when 'people from northern continental Europe brought to the British Isles a language of a kind which had previously been unknown there') with the seventeenth century in North America, when English speakers started to arrive and came into contact with the Native American inhabitants of the continent. I found this quite an intriguing analogy and was wondering if there are any other situations of language contact which might illuminate slighly later events in the history of English, such as the Viking and Norman invasions/settlements. The analogies don't have to be limited to English - any language/geographical area would be of interest! Thanks!

Well, before the Romans, the inhabitants in the areas they moved into were speaking the ancestor of Welsh. That had been affected by Latin by the time the Saxons brought in yet another language, but that in turn was related to what came later with the "Danes", so by then the new "addition" wasn't as foreign. Norman French was quite different grammatically from what had become the native language by then, but it was related to what the church was using, so it was easier for the vocabulary to seep in. Where do you want to draw your lines?

(edited for syntax)