King Arthur

[ItalianStereotype]

see, the thing is NOBODY KNOWS FOR SURE. most credible scholars that I've heard or talked to think the Arthurian legend is complete bunk.

IF Arthur were truly a 5th century king, then no, the technology to make Roman armor wouldn't have been lost. the western empire didn't "fall" until 476 and even afterwards, it took at least one or two centuries for Europe to descend into what we know as the Dark Ages.

all that aside, most historical accounts I've heard of match the Arthurian legend to a 9th century Welsh king/warlord.