The Daleks - S1-E2
Trivia: When originally recorded on 15 Nov 1963, the first episode of this Doctor Who story ('The Dead Planet') was found to be unsuitable for broadcast due to the soundtrack picking up interference from the assistant director's headphones. The episode was re-recorded on 6 Dec 1963, which forced the production of all subsequent episodes (from episode 4 onwards) to be delayed a week.
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