UNIT is a fictional military organisation from the British science fiction television series "Doctor Who" and its spin-off series "Torchwood" and "The Sarah Jane Adventures". Operating under the auspices of the United Nations and initially led by Brigadier Lethbridge-Stewart, its purpose is to investigate and combat paranormal and extraterrestrial threats to Earth. Several UNIT personnel (such as the Brigadier, Sergeant Benton and Mike Yates) played a major role in the original "Doctor Who" series, and it was a regular feature from "The Invasion" (1968) until "The Seeds of Doom" (1976).