Continuity mistake: In episode 3, after the Nitro-9 explosion which Ace uses to blow up the wall, sealing up the mine shaft, the wall is can be seen still standing, unaffected by the blast. However, after a quick cutaway to the Doctor and Ace, the wall has vanished completely by the next shot.
Plot hole: In episode 4 of "The Curse of Fenric", the weather is supposed to change for the worse and become very stormy. The Doctor and Ace are seen to be sheltering under an umbrella from the torrential downpour. Yet the skies in the background are bright, blue and sunny...
Plot hole: The Atlantic Ocean didn't exist in Early Devonian times (c.400 million years ago), so Scaroth's ship could not have been where the Doctor claimed. The Atlantic was formed when Europe and Africa separated from North America around 160 million years ago and is still growing. What is now the sea-bed was once covered up by several miles of Continental Shelf. The Early Devonian landscape would have been far from barren as plantlife was well established by then. So, either the Doctor's theory that Scaroth's exploding ship caused the creation of life on Earth is wrong, or it was much earlier than he said.
Continuity mistake: The mouth panel of the Cybermen costumes was originally intended to be a clear perspex panel. During filming, it was felt that this showed too much of the actor inside the Cyberman costumes. So a decision was taking - mid way though filming - to paint over the 'clear' panel with silver paint. However, this does result in the mouth panels of every Cyberman alternating from 'clear' to 'silver' from shot to shot.
Revealing mistake: During the "cliffhanger ending" at the end of episode 3, it's blatantly obvious that the three columns of advancing Cybermen are merely mirror images of each other. The head of each column has black head bars indicating leadership, and is holding his gun in exactly the same position.
Visible crew/equipment: Just before Dortman leaves to test out his bomb, he comes towards the camera. When he's doing this, look at the right side of the screen - you can see a crewmember's shadow. It can't be Barbara or Jenny because they then enter from the left.Matty W