Johann Schmidt

Johann Schmidt was the eighth incarnation of the Doctor from an alternative timeline where the Nazis won World War II. In this timeline, the Seventh Doctor regenerated after he was shot in the back by Nazi soldiers in Colditz Castle in 1955. Absconding after his regeneration, he adopted the alias "Johann Schmidt" and later told Elizabeth Klein that he had stolen the Doctor's body.

He was able to trick Klein into setting history on its true course by travelling back to Colditz Castle in October 1944. (BFA: Colditz, BFA: Klein's Story)