The Doctor (The Dalek Factor)

An incarnation of the Doctor was trapped on a Dalek-occupied planet.

The Doctor arrived on the world and lost his memory, although he distinctly remembered arriving with someone who was shot by a Dalek. While living in a cave, the Doctor came into contact with some Thals who were infected with the Dalek Factor. The Doctor found a dead snake that had eaten the TARDIS key. His memory returned when he found the key.

The Doctor and the Thals travelled across the planet to find the Dalek Emperor, who revealed that the whole planet was a Dalek research facility for turning Thals into Daleks after the Dalek Factor had passed down enough generations. The Daleks allowed the Doctor's Thal friends to leave the planet thinking that they had escaped. The Doctor's memory was wiped and the Doctor was placed back into the cave where he started to find a new group of Thals to deliver to the Dalek Emperor. (PROSE: The Dalek Factor)

Appearance
The Doctor wore dark trousers and a white shirt. His hair was neat and tidy. When the Doctor's first incarnation appeared as a psychic manifestation, Jomi noticed a similarity in their attire. (PROSE: The Dalek Factor)

Behind the scenes
Though this incarnation of the Doctor is not identified or fully described, the cluster hives' mimicry of his first incarnation and his familiarity with Daleks indicate that he isn't the First Doctor. His use of the title "Professor" suggests a buried memory of Ace, placing this as his seventh incarnation or later.