Brigadier Alastair Gordon Lethbridge-Stewart

The Brigadier is the Commanding Officer to the British section of UNIT (United Nations Intelligence Task Force). The Brigadier first met the Doctor during the Yeti invasion as a colonel and has remained a friend of the Doctor through all of his incarnations (he only met the first Doctor in The Three Doctors). the Brigadier retired and now teaches A-level maths at a boys' school where he had a mental block when the Doctor visited him. It turned out that the Brigadier went back in time with the Doctor and met himself in the past, which caused a massive surge of power and gave the Brigadier a mental block.

The Brigadier was in The Web of Fear: Episode 2 to 6, The Invasion: Episodes 2 to 8, Spearhead From Space to The Claws of Axos (excluding Inferno: Episode 5 where only the Brigade Leader appeared), Colony in Space: Episode 1 and 6, The Dæmons, Day of the Daleks, The Time Monster: Episodes 1 to 4 and 6, The Three Doctors, The Green Death, The Time Warrior: Episode 1, Invasion/Invasion of the Dinosaurs, Planet of Spiders: Episodes 1, 2 and 6, Robot, Terror of the Zygons, Mawdryn Undead, The Five Doctors and Battlefield.