The Brigadier, Benton and Yates are often categorised as companions of the classic series. Personally I disagree. They were regular recurring characters for sure, but they remained at (almost) all times on Earth and in their chosen occupations. They never "left" to go away and travel in the Tardis, unlike every other companion in the series.
Janet Fielding may moan, but she was there when Sarah Sutton, at her own suggestion, spent the best part of her final story wandering around a derelict space ship in her underwear.
