Doctor Who Companion Profile: The Brigadier
Alistair Gordon Lethbridge-Stewart is a Colonel when we first meet him in The Web of Fear. He works with UNIT, the United Nations Intelligence Taskforce, and commands the British contingent, monitoring and defending against extraterrestrial threats. He works well with the Doctor and, when he starts his run with the Third Doctor, he’s been promoted to Brigadier, a title he keeps for the rest of his life (mostly because that’s how fans know the character- he would likely have been promoted several levels above Brigadier). Eventually, after a particularly traumatic experience, he retires, becoming a teacher at a prep school, where he once again runs into the Doctor, and afterward, he goes back to work with UNIT.