Earthshock - S19-E6
Factual error: As the spaceship approaches the Earth of 65 million years ago, the Earth looks very much like the present day one. Hasn't anyone heard of "continental drift"? The Earth's land masses of 65 million years ago were not where they are now. (This has been fixed on the DVD)
Factual error: There are currently well over 700 different native Australian languages, and undoubtedly many more have been extinct for centuries. The chances of a 20th Century European-Australian such as Tegan being able to understand a native Australian language from around 35,000 years ago are so astronomical it is beyond belief.
Earthshock - S19-E6
Factual error: The Cybermen sets four explosive charges around the outside of the door, yet only the middle part of the door is damaged...
Time-Flight - S19-E7
Factual error: The Pleistocene Period began around 1.8 million years ago, not 140 million years ago as stated.
Factual error: In episode 2, the policemen from 1925 recognise the TARDIS as a police call box, even though TARDIS-style police boxes weren't introduced until four years later, in 1929.
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