Factual error: The story is set in 1943. Jean and Phyllis shouldn't readily know who Jane Russell is, as she didn't become famous until her debut film The Outlaw was a box-office hit after the war, three years later. (Although The Outlaw originally had a limited release in the US [but not the UK] in 1943, it was quickly withdrawn by the censors and not released widely until 1946.) True, they could have read about this film in a newspaper or magazine, but considering the strict wartime censorship then in force, it is unlikely.
Factual error: During WW II there would not have been any road signs like the one in the story indicating the way to Maiden's Point: all such signposts were taken down during the war, to hinder the enemy in the event of an invasion.
Factual error: When Kathleen's baby Audrey is revealed for the first time, the baby is clutching a "SuperTed" teddy bear (circa 1984). The story is supposed to be set in 1943...
Factual error: As Jean and Phyllis run into the water to go swimming, they seem to be wearing dark shoes or sandals. But in most of their appearances as Haemovores later in the story, they are wearing bright white (and suspiciously modern-looking) sneakers/trainers.
Factual error: The Naval base that features in "The Curse of Fenric" is supposed to be on the coast of North East England. (A line of dialogue in the story refers to Maidens Bay - two miles from the base - as being in "Northumberland". Yet all the maps and charts on the walls are of the coast of South-East England (Sussex and Kent in particular) which is 250 miles from where the story is supposed to be set.
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