Revealing mistake: When Lancelot is running back down the stairs during the wedding, you can see the sword he uses to cut someone is bending. (00:57:45)
Continuity mistake: When King Arthur threatens to say "Ni!" to the old crone, the left side of his chain mail coif is behind him; before and after that cut, both sides of his coif are draped over his shoulders.
Revealing mistake: In the cave scene, as the knights are arguing about the meaning of the Castle "Aaaargh", the face of a fake Sir Robin is revealed when Lancelot turns his head. That's because Eric Idle, who plays Sir Robin, had to play brother Maynard.
Continuity mistake: The witch's hand changes position from the shot where she is weighed to the close-up of her saying "It's a fair cop" or something like that.
Continuity mistake: When King Arthur arrives and the Black Knight is fighting someone else, the Black Knight stabs his victim straight through the helmet between the eyes. When he removes his sword the sword is through the helmet across his nose, a movement of 90°.
Visible crew/equipment: When they are approaching Castle Aargh. In the next shot after Arthur says "Castle Aargh, our quest is at an end" we can see a motor boat on the lower left corner by the end of the shot. (01:24:15)
Factual error: In the scene inside the Cave of Death, the priest reads the 'Last Words of Joseph of Arimathea'. As he reads them, his eyes go from left to right. If it was Aramaic like he said, he would read it from right to left.
Revealing mistake: When Arthur chops off the Black Knight's first arm, you can see his blade does not slice through the arm, but rather just bumps into the arm, which proceeds to fall off, revealing a fake prop-arm was used.
Continuity mistake: As King Arthur waits to cross the Bridge of Death, the back of his garment is dirty. As soon as he crosses the bridge, it's clean again, and then it's dirty once more.
Visible crew/equipment: In the scene when Sir Robin meets the three headed man, you can just about see the boom mic above them. It is about an inch below the top of the screen.
Continuity mistake: When Galahad is being looked at by the two doctors at Castle Anthrax, his gloves are on. When the doctors lift his tunic to look at the injury more closely, he pushes the tunic back down with now bare hands. They are not shown removing his gloves, and he can't have removed them since he was too busy watching the girls examining him.
Continuity mistake: When the Three Headed Knight asks Sir Robin "What do you want?", you can see one of Sir Robin's minstrels puts the mouthpiece of his recorder into his mouth, but in the next shot, the music plays and he puts the mouthpiece back into his mouth a second time.
Continuity mistake: When the Bridgekeeper is asking Sir Robin the three questions at the Bridge of Death, King Arthur has his right hand on his armour, but when the camera is behind King Arthur, his right hand is now pointing down.
Continuity mistake: When King Arthur tells Sir Bedevere that he is not saying "Ni!" correctly, Bedevere is looking directly at Arthur. When the camera angle changes to behind Bedevere in the next shot, he is now looking at the Old Crone, and in the shot after that, he is looking at Arthur again.
Continuity mistake: When Lancelot storms into the courtyard of "Swamp Castle", in the second shot there's a body in front of the dais that he hasn't even killed yet.
Continuity mistake: When King Arthur fights the black knight, he cuts off his last leg. But when it shows the black knight he doesn't even have a bottom.
Suggested correction: The priest that reads the writing on the wall does read from right to left - his right to left, he reads from the AUDIENCE'S left to right. The camera shot is as if the audience is the wall he is reading from and so his eyes move the correct way for reading Aramaic.
His head moves from the viewer's right to left, which means he's reading left to right.
Bishop73