Other mistake: We see the letter about Merlin being written with a quill. However, despite the length of the letter being written we never see the quill being re-inked. (00:08:20)
Other mistake: When Uther takes Excaliber from Merlin while preparing for his duel with the black knight, we see that Uther is left handed. And he is left handed while writing. He tests the balance of the sword with his left hand, and in fact wears his sword on his right hip in all other episodes. Once he puts his helmet on and begins his duel with the black knight he suddenly becomes right handed.
