The gates are opened by two Clydesdale horses (or similar heavy horse breed). Horses of this type were not bred until the late 1700's/ early 1800's. [The horses were not Clydesdales, but Shires which are one of the oldest English draught breeds and can be traced back to the days of the Roman Conquest.]

Fifth century Saxons never had crossbows, they weren't introduced anywhere in Europe until they came from Asia around the 11th/12th centuries. [Crossbows were used by the Romans in the 5th century AD. See http://science.howstuffworks.com/crossbow.htm. There's also evidence to suggest that the Romans were using them as early as the 1st century AD. In any case, the Romans did have trade ties to China so it's not inconceiveable that the design would have been copied. Crossbows (known as gastrophetes) were also used by the ancient Greeks as early as the 5th century BC. See http://www.answers.com/topic/crossbow. So while the modern design of the crossbow may not have appeared until the 12th century, the weapon itself was very well-known to ancient Europe.]

In pretty much every scene after Arthur and his knights have rescued the peasants and the imprisoned woads from Marius' estate, it's snowing copiously - from a bright blue sky. [Obviously you don't live where it snows much. As I type this the sky is blue here in Michigan and it is snowing.]

In the final battle the defenders use the trebuchets left behind by the retreating Roman army. But trebuchets require a lot of technical experience to use effectively. With the depart of the Roman empire these 'high-tech' weapons had become useless. [The trebuchet is nothing more that a huge sling shot and anyone with a modicum of intellect would soon work out the basics of the mechanism. The effectiveness of their use is indeed pivotal to the sucess of the shot, but not necessary in the working and destructiveness of its use.]

A very common mistake in movies playing in historical times is domestic animals - horses in particular - shown in the film are not coherent with archaeological findings; most often, they are way too big. While few Roman horses of the time the movie is supposed to take place reached a size of 1.6m, most horses of the native tribes were much smaller (about 1.3m) and would nowadays be considered as ponies. The horses shown in this and other similar movies are typical modern sport horses. [While that may be true it doesn't make it a mistake. Movie producers have to work with what exists today. If they tried to claim the horses where factual representation of horses of the era, then it would be a mistake. As such this is only historical trivia.]

When Guinevere and Arthur are kneeling over the dead Lancelot, there are two shots directly on Lancelot. In the first shot, he is slightly smiling, but in the second shot you can see a definite grin. [Absolutely incorrect. Just to be certain I carefully checked both versions of the movie, standard release and Director's Special Edition and it is simply the way Ioan Gruffudd's mouth is shaped that could possibly give you the illusion of a smile, but certainly not me. There is no hint of an upward curve at the corners of his mouth what-so-ever, his cheeks are completely relaxed, as are the corners of his eyes and absolutely no sign of a smile at all. No mistake here.]

They did not have contacts back in that period, but you can see that Keira Knightley is wearing hers in the scene where Arthur sets her broken fingers. [I could not see it going frame by frame on my 32" TV.]

The Battle of Badon Hill must have occurred near a hill, as the name says, and not in front of Adrianus's Wall where there is no hill anywhere, as we can see in the final battle of the movie. [Not necessarily a mistake, it happens quite a lot that battles are named after locations where they did NOT take place. For example: the battle of Issus, where Alexander defeated the Persian king Darius, took place nowhere near Issus. And the battle of Zama, where the Romans defeated Carthage in 202 BC, occured miles away from Zama. ]

The Saxons are seen coming with a large fleet to Britannia. This is not true because the Saxons came ship by ship to Britannia, and not with a large fleet. [Not so. Saxon raiding parties had been terrorising Britain from the late 4th century AD. At first, they simply conducted hit-and-run actions. Later larger campaigns followed, involving larger armies, which certainly required multiple ships for transportation. We know that a considerable Saxon army was present at Badon Hill, so it is most likely it came to Britain in more than just one ship.]

Guinevere's left hand fingers were dislocated in the cart scene and Arthur puts them back in. This happens in daylight. The same evening, Guinevere is able to use a bow even pulling the string with her wounded left hand. This would not be possible. [Many times on a rugby field I have seen players dislocate their fingers and have them snapped back into place. In most cases they carried on playing. It is certainly painful but if your life was at stake you would probably have enough incentive to fight through the pain.]

After the initial battle, the Bishop sees Arthur and his knights and is surprised that there are "so few of you." and yet the Bishop knew exactly how many pardon-scrolls to bring. [If you look at the door into to the hall where the round table is, there are two Roman guards and they are each holding identical boxes of scrolls like the one that the priest picked up before leaving Arthurs room. So the Bishop obviously had brough more with him for all the knights.]

The weather in the film is portrayed as wintry throughout with snow, ice and blizzards. Yet the tree climbed by the English spy (shortly before he's shot out of it by one of Arthur's Knights) is an oak tree in full leaf that looks like it was filmed in mid-summer. Similarly at one point there is snow falling, yet with a background shot of blue sky. [Weather is unpredictable. I live in Michigan USA and I can tell you I have seen snow falling when it is sunny with blue skies and green trees.]

Did it escape anyone else how the doors in Hadrian's Wall changed their ease of use? Early in the movie, we're shown the doors opening, and they're made out to be these great, ponderous things that take a long time to open. First the soldiers have to take a heavy mallet to prize free the huge wooden bar holding them shut, remove the bar, and then two huge Clydesdale horses are required to slowly pull them open and then the doors slowly open. And yet in the final battle against the Saxons, Arthur is somehow managing to open and close these doors pretty quickly, and several times in a row, no less. Not to mention how he (or someone else on the good guys' side) now seems to have the ability to remotely operate these doors, making them close behind the Saxons after they enter. [This is because the first time the gates were opened, it was supposed to be the first time in many years that anyone had gone through them. Note the rust that explodes from the hinges the first time they're opened. Later on, the gates had been back in use, and would've been a lot easier to open and close.]

After the first battle scene, when Arthur and the Bishop are talking, An unmounted horse is seen behind them. The camera cuts away and then cuts back and the horse is gone. This happens just before Lancelot says "He's called Merlin, the black magician." [Someone probably moved the horse or it moved itself. It isn't just going to sit there all day.]

When the leader of the Saxons goes to put his sword back in his sheath after he kills the man who was trying to rape the woman, there is no blood on his blade. [He didn't stab the man, therefore, there would be no blood on the sword.]

Jols, the Sarmatians' quartermaster, seems to appear from nowhere and disappear again several times. [Jols rides with the Knights to rescue the family. Although it does seem he pops out of thin air in various scenes, he's been with them the entire time.]

Prior to the last battle, as the knights are preparing to turn back and join Arthur, Lancelot's twin swords hang from his back and show very modern octagonal screws attaching the pommel to the handle. [Although they do seem to look like screws, it isn't. You can't see them very but they are just plain bolts holding them together.]

When the knights leave on their quest to save the Roman family, they leave alone; then, at the estate, the Bishop's assistant suddenly appears, with no explanation as to how he got there. [I thought the same thing. While it looks this way, the Bishop's assistant did ride to the estate with the knights. His horse is seen briefly in the back of the line as the knights are riding cross-country. You really have to be watching for him in order to see him.]

When Merlin's warriors trapped Arthur and his men in the forest, they used barbed wire. Barbed wire was invented in the United States in the mid 19th century. [They used barbs from trees and wrapped them together to look like barbed wire.]

If even hardened troops were afraid to go north of Hadrian's Wall, it is highly unlikely a noble Roman family would be up there - outside the protection of the Empire - living in an unfortified villa with just a handful of guards. [It wasn't just a "noble family" living up there. They were missionaries, who have always lived in dangerous areas since the beginning of Christianity.]