Revealing mistake: Geoffrey Hinsliff (playing Fisk) accidentally refers to Tryst as "Fisk" at one point.
Revealing mistake: During the whole story, Tom Baker is struggling not to laugh at Tryst's completely made-up accent.
Revealing mistake: In episode 1, watch out for the wires pulling K-9 along the beach. (Unlike a real dog, K-9 didn't take well to the soft sandy surface and sank into the sand. Pulling K-9 along on wires provided an illusion of movement when the motor inside wasn't up to the job).
Revealing mistake: The Grove is one of the most obvious indoor sets masquerading as a lush outdoor environment. The sound the actors' feet make on the floor is especially unforgivable.
Revealing mistake: When the Keeper is on the TARDIS, he asks to borrow the screen. But on the upper left corner, you can see it over where it's meant to be.
Earthshock - S19-E6
Revealing mistake: When the Cybermen break through to the bridge, they brush against the door and it bends as if made of cardboard. It was supposed to be made of reinforced steel. (01:09:10)
Earthshock - S19-E6
Revealing mistake: Just before the Cyberman fires on the console, you can see Adric trying to keep as far away from it as possible before it explodes. (01:35:05)
Earthshock - S19-E6
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.
Earthshock - S19-E6
Revealing mistake: When Lieutenant Scott kills the second Cyberman on the bridge, he starts falling down way too early.
Earthshock - S19-E6
Revealing mistake: The "dead" crewmembers at the end of episode two can be seen breathing.
Revealing mistake: When a Cyberman's arm is sliced off by the Robot's shuriken, you can see his real arm bulging out at the right side of his body. (01:00:25)
Revealing mistake: When the crack in the wall breaks open, the wall wobbles rather obviously.
Resurrection of the Daleks - S21-E4
Revealing mistake: When Lytton and his men approach the self-destruct chamber in episode three, the door is closed in front of them. It wobbles as it closes.
Resurrection of the Daleks - S21-E4
Revealing mistake: When the Doctor is shooting the Dalek creature hidden under the coat, he is obviously using blanks because when you see the coat there are no bullet holes in it.
The Caves of Androzani - S21-E6
Revealing mistake: When Stotz cuts a hole in his ship's door, you can see that the inside of it is made of white polystyrene. They painted the outside of it but obviously forgot about the inside. Also listen to the sound it makes when Stotz punches the hole through - it sounds exactly like polystyrene.
The Caves of Androzani - S21-E6
Revealing mistake: It's already been mentioned that Peri bounces off a mattress, but watch what happens when the Doctor walks over to see if she's all right. The 'cave' floor visibly moves under his foot.
The Caves of Androzani - S21-E6
Revealing mistake: When the Doctor is looking for a way to break through his manacles, he brushes against the machine with the bright light that he eventually uses to cut them. When he does, it wobbles when it obviously should remain motionless.
The Caves of Androzani - S21-E6
Revealing mistake: In the very first shot of Morgus' hand-held computer, it's obvious it's a TV remote. Look for the controls for contrast and tint.
The Caves of Androzani - S21-E6
Revealing mistake: When Peri falls into the spectrox nest, watch for her to reappear as she bounces off a mattress.
Revealing mistake: The bottle of acid that the Doctor throws at Mestor breaks open well before it hits the shield that Mestor is projecting around himself.
Answer: In 'The Five Doctors', three separate Cyberleaders are definitely used. So it's likely that Cyberleaders are like unit commanders, of which a fair-sized army might have several.
Daria Sigma