GreenInkling
Who was the Brigadier? I don't know or don't remember.
He was one of the classic companions, and I mean CLASSIC. Brigadier Lethbridge-Stewart was one of the founders of UNIT, and essentially the Doctor's boss for a while. He knew the Doctor from his Second to Seventh incarnations, and... oh, screw it, here's the Wikipedia page: [x]
Basically, though, Nicholas Courtney (the actor who played him) died earlier this year (just before Elisabeth Sladen, I think), and I just found it very moving that they payed tribute to him in this episode.