A thing that stroke me through the early Tom Baker episodes of Doctor Who, was that the Doctor would sometimes act with something resembling impatience towards UNIT officer Harry Sullivan the nature of whose offences I never really grasped. Some people, I'm sure, would brush it off as an insignificant and trivial detail -- but then, what are internet forums for if not for trivia? Other people would probably brush it off as the the Doctor being jealous because Sarah sometimes spoke about Harry without animosity.
In particular, there was a scene in The Ark of Space where the Doctor cast a very impatient glance at Harry -- and unlike usual it seemed to be to be unexplained. Some people say that Doctor was jealous about some sort projected romance developing between Sarah and Harry, but to this I just say "Pfew". I don't really know why I say "pfew", as the word doesn't seem to be registered in the Oxford Dictionary, but there it is.
So, as I'm currently trying to finish my ph.d. about the "Relationships between the Doctor and Early Male Companions beside the Obvious Female Damsels in Distress", might you have any light to shed upon the issue of the Doctor's lesser than usual friendliness towards mr. Sullivan?