Why do the cast of Excalibur (1981) have full plated armor when that didn't exist back then?
Is this due to stereotypes about King Arthur and knights in shining armor? This was supposed to take place around the start of the Dark Ages, after the Romans left. But I don't think I've ever seen Romans depicted in such armor, which would probably look silly.
In short, the filmmakers were very well aware that the armour used in the film was both anachronistic and fanciful. Their principal armorer (Terry English) told them at the outset what 6th Century armours should look like and there was a conscious decision made not to go in that direction.
Terry English: Well, John [Boorman, the director] said to me and kind of sparked off visually, it's a building thing, and he said "I want them to look like American footballers, with these big shoulders and stuff"
Adam Savage: How accurate do you look to get? I mean because King Arthur is supposedly from the sixth century, right? Yeah, I mean clearly Boorman and you were taking from all sorts of different periods. What was your jumping-off point? Does he tell you "I like this kind of armour, I don't like that kind of armour"?
TE: Yeah, kind of what we did though because there was a lovely guy, Tony Pratt, who is the production designer and we, me, and him and John went to the Tower of London and spend an afternoon there looking at original armours with sketch pads and stuff to get various ideas and blah, blah, blah ... and it kind of always just progressed from there. I mean Tony and I got together and we did sketches of all of them ... and it just kind of happened from that.
At the end of the day, the director wasn't overly fussed about historical accuracy. The main character is mythical and stories about him stretch over centuries of retelling in any case. The important thing to him was to make a film that audiences could relate to.
“If there was ever an Arthur,” Boorman says, “he’s sited in about the sixth century. But the date is the least important thing really. I think of the story, the history, as a myth. The film has to do with mythical truth, not historical truth; it has to do with man taking over the world on his own terms for the first time. So the first trap to avoid is to start worrying about when or whether Arthur existed. The stories that inspire us were really fifteenth-century works, by Thomas Malory and the rest, looking back nostalgically on the twelfth.”
‘The Past, Present and Future of Humanity’: John Boorman’s ‘Excalibur’
