Continuity mistake: In the scene where Ademar is in France with the Free Companies, it is raining fairly heavily at the beginning of the scene. In the following shots, showing just Ademar and his squire, there is no rain visible, just fog in the background. After Ademar stabs the knife through the tournament result sheets, there is another wide shot, with rain again visible. (01:09:10)
Continuity mistake: When Chaucer is introducing William at the end of the movie, he stands on the arms between the chairs of Prince Edward and the lady, a foot on each arm. When it cuts to a side view showing William's father to the Prince, Chaucer is no longer in between the chairs. Not to mention the fact that the Prince is looking at the railing (where Chaucer just was). The very next shot, he is back between the chairs. (02:03:05)
Continuity mistake: As the scene in which William is knighted begins, Roland takes a position to his right, holding a staff in both hands, raised to his right. Once the Prince reveals himself and approaches, Roland has the staff touching the ground, which is fine, he may have done that as a response to the Prince. Cut to a close-up of Roland's face an instant later, now he looks worried and the staff is raised to his right. Cut back to the Prince an instant later, and the staff is back on the ground.
Continuity mistake: In the Paris tournament, when William stops losing and starts winning, the 3rd knight he faces (the one whose helmet he knocks off) sets off with his lance in his left hand, but it switches to his right. Also, in the shot from behind the opponent, William moves his lance away from his adversary as they ride by. (01:22:25)
Continuity mistake: When Sir Ulrich first battles Count Adhemar after the first hit Sir Ulrich is taking to Roland stating how hard he hits. The camera angle from the front shows his arm bent in front of him but the camera angle from the back shows his arm resting on his leg. Happens about 3 times during the entire scene. (00:45:40)
Continuity mistake: When William is riding through the streets of London, Roland is shown walking in front of him. Next it shows Wat, Chaucer, and Kate walking behind him closest to the wall on the left. The next shot shows people on their left. Then it switches back and forth a few times. (01:34:05)
Continuity mistake: In the scene where Ulrich first rides to compete as Sir Ector ("We Will Rock You" is playing), there are various shots of the crowd enjoying the song. The woman seated to the right of the tournament sponsor (as you look at the screen) has a Princess Leia-type hairdo. Her buns sit high on the sides of her head in one shot, down lower in the next shot of her, and back up high in a third. (00:03:55)
Continuity mistake: When William is let out of the stocks you see him take his hands out of the holes, however in the next shot you see him take his hands out of the holes again. (01:53:30)
Continuity mistake: In the part before the world championship, when everyone is trying to convince William to run away to avoid capture, the front edge of the large shoulder plate of his armor is in front of his breastplate in some scenes, and behind it in others. He stands virtually still during the scene, except for turning slightly. (01:44:20)
Revealing mistake: In the joust montage sequence when William allows himself to lose repeatedly in order to prove his love: Just after the shot of the white flags going up, we see "William" get hit again but it reveals itself to be a mechanical double first in the way it folds over backwards in a sharp 90 degree angle (no human can bend that way), and it reveals that there isn't a person within because it breaks with the lower portion of the "body". Shot from another angle (the right) the front portion of the saddle blocks this from view.
Factual error: Ulrich's armor repair is either gas welded or arc-welded, not Forge welded. Forge welding is the only type of welding available at the time and is usually extremely different if even noticeable. (00:35:10)