General (formerly, and most well known as, Brigadier) Sir Alistair Gordon Lethbridge-Stewart (commonly nicknamed The Brigadier or The Brig) was one of the founders of UNIT and commander of its UK operations. From his second incarnation onwards, and notwithstanding some early tension between the two during the start of his third incarnation, the Doctor long considered the Brigadier one of his most trusted human allies and closest friends.
The then-Colonel Lethbridge-Stewart was the second commander of the British Army forces during the Great Intelligence's assault on London, replacing the deceased Colonel Pemberton. He was the sole survivor of a Robot Yeti assault at Holborn before heading down to the London Underground to take command. Here, for the first time, Lethbridge-Stewart met the strange little man known as the Second Doctor. Lehtbridge-Stewart showed a quick, decisive manner, and a ready acceptance of events, even believing the story about the TARDIS from the start.
Little was shown of Lethbridge-Stewart's life outside UNIT in the television series, though Planet of the Spiders referred to a relationship with a woman called Doris, whom he later married. Most of the Third Doctor stories were set on Earth and feature UNIT and the Brigadier heavily. While not as ubiquitous in the following years, he appeared alongside every subsequent Doctor in the original television series run with the exception of the Sixth Doctor (though he did meet him in Dimensions In Time).
Lethbridge-Stewart's last appearance in a Doctor Who television episode was in 1989, in the Seventh Doctor serial Battlefield. Called out of retirement to deal with an other-dimensional invasion of armoured knights led by Morgaine, he found himself once again at the Doctor's side. Lethbridge-Stewart served as his world's champion as he faced down and killed the demonic Destroyer of Worlds armed only with his service revolver and a load of silver-tipped bullets.
Although Lethbridge-Stewart never appeared in the revived series, the character is still alive during the Tenth Doctor's tenure. In the spin-off series The Sarah Jane Adventures story "Revenge of the Slitheen", Sarah Jane Smith says to "give [her] love to the Brig". In the Tenth Doctor episode "The Poison Sky", the Doctor mentions that he could use "the Brigadier". He is then told that "Sir Alistair" is "stranded in Peru", indicating that the Brigadier has been knighted. In 2008, Courtney again reprised the role in a The Sarah Jane Adventures story, "Enemy of the Bane", and confirmed his knighthood repeatedly: Major Kilburne and Sarah Jane each address him as "Sir Alistair" and he later introduces himself fully as "Brigadier Sir Alistair Gordon Lethbridge-Stewart" to Mrs. Wormwood.
In his old age, the Brigadier has developed a dislike for the new way UNIT works and often refers to events that happened in "his day". He walks with a walking stick now, but is seen driving a Bentley to UNIT's "Black Archive".
