From CBS News:
The BBC reports Nicholas Courtney, best known for playing Brigadier Alistair Lethbridge-Stewart - known more commonly as "The Brigadier" - on "Doctor Who" has died in London at the age of 81.
Courtney played opposite five actors who played Doctor Who on television, reports the BBC. But he made his first appearance in 1965 on the show as a different character, Bret Vyon.
When the actor returned to the show three years later he made his first appearance as the Brigadier. He made his final appearance on "Doctor Who" in 1989, according to IMDB.com. He reprised the role on the show "The Sarah Jane Adventures" in 2008.
In June of 2007, Toobworld Central honored Courtney's portrayal of the Brigadier with the Birthday Honors List entry into the TV Crossover Hall of Fame.
June 5, 2007 - THE BIRTHDAY HONORS
At the time, his membership needed that "What I say, goes" push via the Birthday Honors. However, a year later he appeared on 'The Sarah Jane Adventures' in the role and made his qualifications legitimate. (There was also an appearance on the Harry Hill variety show back in 2000, which gave him a presence in the Skitlandia TV dimension.)
I still hold to the "By Any Other Name" theories that Courtney's character in 'The Avengers' was also Alistair Gordon Lethbridge-Stewart, as was one of the young street urchins in the 'Doctor Who' episodes "The Empty Child" & "The Doctor Dances". With that theory, the Brigadier has met every incarnation of the Doctor save David Tennant's, Paul McGann's and Matt Smith's. (I'm told that there's at least one audio-play in which Courtney and McGann work together, but that belongs in a different universe based on Mankind's creative spark.) On a technicality, he did meet the First Incarnation of the Doctor, but played by Richard Hurndall in "The Five Doctors", not the original played by William Hartnell.
Here's a YouTube video celebrating both the actor and his most famous character:
I salute you as well, Sir. Good night and may God bless.