And the direction in which he was walking.
And the pyjamas with the unusual detail at the ankle
And the urgency with which he was walking
And the fact that the little girl was being carried in an awkward and very tiring way. Which no experienced father would use. Tannerman was never a father, by which I mean that he had never hung around to help bring up any of his possible offspring. Tannerman didn't know how to carry a young child.
Had it been Dr Totman and his little girl returning to his flat, then he would have been walking in front of Jane en route to his flat. Cos Janes flat involved a walk in the westerly direction as did Tannermans.
Even you disbelievers cannot reasonably claim that Jane could have thought that the man was walking tangentially in an easterly direction, to her northerly direction, when in actual fact he was walking in a westerly direction ... and was closely preseding her for a substantial distance en route to his flat. Can you?
I don't believe any of you are that thick.