Tom Campbell was a Police Constable from London, he accidentally boarded the TARDIS mistaking it for a genuine Police box while attempting to foil an armed robbery. After returning from a journey with Dr. Who he was returned to the scene of the crime earlier than he left, therefore allowing him to apprehend the robbers. (Movies: Daleks - Invasion Earth 2150 AD)
Behind the scenes
Actor Bernard Cribbins, who played Campbell, would later appear on the TV series proper as recurring character Wilfred Mott.