The Web of Fear: Episode 4, at 1.13, you get the first, known, extant, moving image of Brigadier Alistair Lethbridge-Stewart. At 8.13, he establishes why he will be with the Doctor for the rest of his life.
What are you doing on November 23rd (assuming you are not in the UK)? I’m considering buying basic cable for a single month. The eldest daughter is pushing hard, and time is ebbing away.