I always thought that the Normans ensured that Norman would be used by importing a newish top-down management from the continent.

In a manner of speaking, yes. When Will-babe's hangers-on carved up the New Territories among them they brought in Norman and French "managers" - mostly clerics - to wring the max moolah out of the long-suffering Anglo-Saxon peasantry. The outcome of that was the English feudal system, of course, but as a precursor they replaced Anglo-Saxon with French and Latin in the local shire and hundreds courts. This ensured that the landlords understood legal proceedings even if those being proceeded against didn't ...

There was some balance, though. It suited the Norman overlords to keep many of the traditional rights intact and these were considered when cases were being adjudged. This, eventually, gave rise to the common law as we know and ?love? it.