Marco Polo - S1-E4
Other mistake: In episode seven, Kublai Khan refers to backgammon as a game of cards....obviously he's not an experienced backgammon player.
Other mistake: William has a bit of a nightmare, completely throwing the others during one scene by saying the same line ("It's not very likely") twice, and fumbling the line "You knocked both Susan and I unconscious". He also omits the scripted explanation for the melted clocks.
Other mistake: In episode one, when the crew wonders what The Sensorites will do them, the camera zooms in on the Doctor as he says, "or kill us?". It then jerks with an audible click as though hitting something.
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