Hi David. Here is an interesting quote from the net to describe the complicated linguial history of England:
English is a 
West Germanic language that originated from the 
Anglo-Frisian dialects brought to 
Britain by 
Germanic invaders from various parts of what is now northwest 
Germany and the 
Netherlands. Initially, 
Old English was a diverse group of dialects, reflecting the varied origins of the 
Anglo-Saxon kingdoms of England. One of these dialects, 
Late West Saxon, eventually came to dominate.
 English changed enormously in the Middle Ages. Written Old English of  1000 AD is similar in vocabulary and grammar to other old Germanic  languages such as 
Old High German and 
Old Norse,  and completely unintelligible to modern speakers, while the modern  language is already largely recognizable in written Middle English of  1400 AD. This was caused by two further waves of invasion: the first by  speakers of the 
Scandinavian branch of the Germanic language family, who conquered and colonized parts of Britain in the 8th and 9th centuries; the second by the 
French Normans in the 11th century, who spoke 
Old Norman and ultimately developed an English variety of this called 
Anglo-Norman. About 60% of the modern English vocabulary comes directly from 
Old French.
[1]
 Cohabitation with the 
Scandinavians resulted in a significant grammatical simplification and lexical enrichment of the 
Anglo-Frisian  core of English. However, this had not reached southwest England by the  9th century AD, where Old English was developed into a full-fledged  literary language. This was completely disrupted by the Norman invasion  in 1066, and when literary English rose anew in the 13th century, it was  based on the speech of 
London, much closer to the center of Scandinavian settlement. Technical and cultural vocabulary was largely derived from 
Old French, with heavy influence from 
Norman French in the courts and government. With the coming of the 
Renaissance, as with most other developing European languages such as 
German and 
Dutch, 
Latin and 
Ancient Greek supplanted French as the main source of new words. Thus, English developed into very much a 
"borrowing" language with an enormously disparate 
vocabulary.
Yes, the royals did speak German as a common language. The palace did change when Victoria learned English as a youngster.
English varied greatly around the countryside, even as did the dialects of my day, which was up to 1948 when I came to Canada.
Even in public school(private to North Americans) I was taught English, German and Latin from an early age.
It is interesting how English developed over the years, and how much it changed from period to period.
Cheers,
Jim