Out of interest, do non-British English readers understand "Map key" as a synonym for "Legend"? I've always called it a "key" (as a British English speaker) but Americans often don't seem to understand this.
American here, I've heard both "Map Key" (or just key) and "Legend" used interchangeably for map Keys/Legends for as long as I can recall. So I suppose there's more to it than just American vs. British English.
Legend is the more common usage in the US in my experience. Map key, like car park, seems a bit more awkward to American ears but is self-explanatory and obvious in it's meaning.
