Trivia: Location filming of "The War Games" took place in East Sussex during April 1969. To depict the desolate landscape of "no-man's land" during 1917, the location shoot was done at the Brighton Corporation Refuse Tip at Sheepcote, near Brighton. The very same location had been used just a few months before, also to depict "no-man's land in 1917" by Richard Attenborough, for his film Oh What A Lovely War.
The Invasion - S6-E3
Trivia: The episode was intended to prove that Earth-based stories could be produced cheaply and effectively. Ironically, it was the most expensive Doctor Who episode ever produced when made, and remained so for several years.
Trivia: In one or two of the location filming scenes, Zoe is seen in the background struggling to hold her trousers up. Her belt broke, but filming was so far behind that the director said to carry on.
The Invasion - S6-E3
Trivia: In the animated reconstruction, released in 2006, the words "Bad Wolf" can be seen on a wall at one point. The phrase was a major plot point in the first season of the new series, where it turned out in the season finale, "The Parting of the Ways", that companion Rose Tyler had scattered them across time and space as a message to herself while temporarily possessing the power of the entire Time Vortex.
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