But everything in the classic Arthurian stories is anachronistic. When Chretien de Troyes and Thomas Malory and the rest told their tales of knights errant they were importing what were to them contemporary (or recently past) values, technology, and society into what was supposedly a fifth- or sixth-century setting that would in reality have been wildly different. And that’s even before you get to all the, you know, magic and dragons. Malory didn’t care about anachronism when he filled post-Roman Britain with French-speaking aristocrats jousting in plate armour. Merlin was just doing exactly the same thing.
I've seen the story of Arthur presented in a variety of ways. There's the Disney stuff, which I saw a long time ago and don't remember clearly.
I had to read Morte d'Arthur in college and most of it sailed over my head because that was a few years before I became hooked on Dragonlance and discovered that I actually enjoy some kinds of fantasy besides basic D&D and the Fighting Fantasy gamebooks.
I'd seen Camelot on TV (the musical) and just sat back and enjoyed the music. The story didn't make much sense at the time. Years later, I joined the Society for Creative Anachronism and learned so much more. The after that, I worked on a production of Camelot... and was bemused at how much they got wrong (I wasn't in any position to influence that, since my job was on the dressing crew).
I helped Lancelot in and out of his costumes since most were quick changes that he had no time for if he had to go downstairs to the dressing room, so he had to be changed in the wings in very dim light, very quietly... and one night a fastening on his breastplate gave out. It popped right on stage, during a quiet scene that had conversation, rather than music. As he exited stage left, his armor went
creak... creak... creak... with every step. The actor held it together until he got past the sight lines, while the rest of us in the wings (the stage crew and me) were trying desperately not to laugh.
Then he grinned a huge grin, and I promised to get it fixed during intermission. I snagged Arthur's dresser to come help, and told her we should check Arthur's armor and also Pellinore's (Pellinore didn't have a dresser, but should have; he had a really fast change that kinda mattered since his back-to-back scenes took place 5 years apart in-story).
A trip to the scene shop later, we discovered that yep, Arthur's armor would have popped soon. Pellinore's wasn't quite as bad (fewer scenes), but it would have happened eventually. So we fixed all three... in 20 minutes. They held up throughout the rest of the run.
After the show opened, a couple of people from the SCA group went to see it and at the next Arts & Sciences meeting we had, they proceeded to tell me everything wrong with it, from the ridiculous heraldry that wasn't remotely accurate, to the set design, to the costumes, to the armor... yeah, the armor was bad for accuracy. I pointed out that these were actors who had to be able to move, sing, and dance, and weren't used to doing that in the same kind of armor that fighters in the SCA wear (yes, knights in the SCA are expected to be able to dance while wearing armor; I witnessed that for myself during a principality tournament).
So there was a reason the Camelot armor was made of plastic. Thank goodness it was, since I wouldn't have had a clue how to repair it if it was made of metal. But at least thanks to my time in the SCA, I knew what all the armor pieces were, and where they were supposed to go, and explained it to the others on the dressing crew and a couple of props people who had the mistaken notion that armor is a prop, not a costume. I never sent Lancelot out on stage dressed incorrectly (Arthur was sent out in a mishmash of clothes one night, without shoes; the props crew had moved them without telling Arthur's dresser and she couldn't find them - so she grabbed some stuff, got him into them, and got him out on stage in the nick of time; he never questioned her about this as the actors with dressers came to rely on us).
I live just a few miles from the actual grave of King Arthur (um, possibly), so the history of Arthurian myth-making is vividly present!
(It’s a short walk from the Isle of Avalon, but Camelot’s a bit of a way down the A303 and hasn’t aged well.)
Some of the Merlin fanfic stories I've read say that Camelot just wore away over the centuries, partly due to being plundered for the stone to make other buildings, and partly due to the normal ravages of time when there's nobody around to keep it repaired. Others say that Merlin enchanted it and hid it away so it's been kept in shape for when Arthur returns.
There's a story in which Merlin owns a place near the Isle of Avalon and the town there is basically a tourist attraction for Arthurian afficionados. It's just after the annual festival when Arthur finally turns up, having crawled out of the Lake, and finds himself in a coffee shop where he can't understand anything being said around him or to him (they take him as one of the role-players who maybe didn't realize that the festival just ended).
When Arthur speaks to them, it's not in modern English. It's in Brittonic. I applaud the author for showing the readers that it doesn't make sense for Arthur and the knights (the other knights aren't in this particular story) to come back and immediately understand modern English, including idioms.
I know there are lots of anachronisms in Merlin. There are some I shake my head over, others I'll mock (like Morgana's dress). I've even noticed that every adult male in Camelot, including those just visiting, wear the exact same color and style of trousers. That's probably a costume budget decision, but it stands out to those of us who notice such things. Gwaine first appears in Season 3, episode 4. He leaves at the end of that episode, having been banished by Uther. All through that episode, he's wearing the same color and style of trousers that the Camelot knights wear. In the context of the story, it makes no sense at all. He then turns up in the 8th episode of that season (leaves again because he's still banished), and is knighted in the 13th episode (a two-parter involving the Cup of Life and trying to get Morgana off the throne; Arthur decides to knight several commoner men - and never knows that Gwaine is actually not a commoner). Some fans have said the Cup of Life is the show's take on the Holy Grail.
Since Merlin is immortal and is supposed to have waited 1500 years+ for Arthur's return, it's obvious that the show is meant to take place in the 6th century. But there are so many anachronistic elements that you pretty much have to say, "Okay, this is alt-history where tomatoes somehow made it to Britain centuries before they actually did and people can get thrown across the room and into trees and never have to worry about concussion."
That said... now that I've read more about this period of history (ended up on Wikipedia, searching out names for a story I'm writing that takes place in 11th-century Britain, and went down a rabbit hole of links and ended up reading about the 7th century or thereabouts), it would be interesting to see the actual sites where the stories are said to have happened.