Other Mentions
The Brigadier is mentioned by the Fourth Doctor in The Android Invasion and by the Fifth Doctor in Castrovalva and Time-Flight. A vision of him is seen along with the Doctor's companions aside from Leela on the scanner screen in Resurrection of the Daleks. He is also seen calling out to the Doctor just before his regeneration in Logopolis.
Read more about this topic: Brigadier Lethbridge-Stewart