The English language, like Romanian, Romansh, Ottoman Turkish, and Siculo-Arabic, is known for its extremely wide and vocabulary of differing etymologies, and analytical non-inflected grammar, due to England's history of being conquered many times, as well as England conquering many other countries in turn, and receiving cultural, legal, and linguistic influence in many different directions.
Obviously, in any timeline the English Channel would assist invasion, and like the North Sea would be more of a highway than the barrier. But let's say we handwaved that away and somehow made England isolated from the European and Avalonian continents.
What if none of the conquests happened except for the Norman conquest? After that, a Norman-descended England would maybe invade its neighbors (such as France and Frisia), but never conquer them. Middle English would settle on a Germanic substrate and Norman-French superstrate. Greek and Latin would filter in later. Early Modern English would then develop directly from Middle English. We could also prevent the Danish and Wendish settlements that occurred before the Norman conquest but this is not required.
What do you predict that English would look like if this had happened? And what would the role of England have been, would it still become a regional great power without being so constantly militarized and connected to continental realms?
(As you can see, I wrote this in a fake version of English with no Slavic, Celtic, or Altaic words.)