Trivia: Sylvester McCoy was given a new costume for Season 26, with a darker jacket, hatband, tie and handkerchief to reflect the gradual development of the Seventh Doctor's personality, and to show that the Doctor himself was getting 'darker' and more serious. To surprise viewers with the revised outfit, it was decided the Doctor would begin the season wearing a duffel coat over his regular clothes, the belief at this time being that "The Curse of Fenric" would be the 'lead story' for season 26. Later however, it was pushed back to third in transmission order, meaning that the effect went for nought, as the costume had already been seen in the first two serials.
Trivia: Watch closely the scene where the Haemovores come out of the sea en masse, and pay particular attention to the two 'child' Haemovores at the back of the group. Those two were Sam and Joe Kent-Smith, who are Sylvester McCoy's sons. They'd come down to the location filming to watch their father working, and found themselves 'roped in' to the filming to boost the numbers of Haemovore monsters.
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.
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