Actually, Les, most indications are that emigration of Angles and Saxons to Britain was relatively small in comparison to the total population; in other words, the majority of people in Britain are still Celtic by heritage, descended from Celtic speakers. (The few DNA studies that have been done on bog bodies and the like support this.) So while you're right that the British situation was not one of political domination from a far-off land, it WAS one of political domination from a small minority population resulting in wholesale adoption of the dominant language throughout most of Britain (remembering that Scots is also derived from Anglo-Saxon). It is not hard to imagine a small minority population of Germans settling in England and enforcing German-only education. This is what the English did in Ireland, and it worked pretty well. I'm not saying it is likely, but it is entirely possible.