The Doctor proudly carries the rifle, boasting that it's made in Birmingham. But in The Pyramids of Mars, Episode 1, he said he never carries firearms.
A headline on the newspaper lining Litefoot's linen basket mentions Denis Healey, who was Chancellor when the episode was filmed, some 90 years after it was set.
The Doctor indicates the course of the Fleet when he mentions the Thames, and the course of the Thames when he mentions the Fleet.