Sidney Harris

Private Sidney Harris was a member of the Britischer Freikorps under Lieutenant Anthony Rupert Hemmings in an alternate timeline.

In 1951, he and Private George Brady were assigned to patrol the Festival of Britain, where they intimidated Harry Gold and tried to extort money from him. They were stopped by the Seventh Doctor who, pretending to be an authority figure, ordered them to return to their unit and place themselves under arrest. (PROSE: Timewyrm: Exodus)

Behind the scenes
Sidney's first name was also given as Sydney in the novel.