Marco Polo - S1-E4
Trivia: This, the fourth Doctor Who story, is one that did not survive the BBC's purging of the archives in 1972-78. Originally seven episodes were made, and first broadcast in February-April 1964: none survive in the BBC's archives, and the entire story is one that is "missing believed wiped"
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