"I only met Nicholas Courtney once and very briefly - but he was as kind and generous and funny as his reputation suggests. And on screen, his perfectly pitched performance as the Brigadier carved a very special place in the history of Doctor Who. Not just because he could be grave and funny at the same time, and wise and silly in the same moment, and not just because you could still love him when he was clearly in the wrong, or because he could point a gun at you and still somehow twinkle - but because out of all the people the Doctor has met, in all of space and time, Nicholas Courtney’s Brigadier Alistair Gordon Lethbridge-Stewart was the only one who was ever his boss.
Somewhere out there, the Doctor just got a little lonelier.”
- Steven Moffat