Season 16, 1978, 4 episodes
Fourth story in the Key of Time series. The Doctor and Romana split up immediately and Romana is captured by the evil Count Grendel, who is using android duplicates to try to seize the throne. The Doctor and K9 have to rescue Romana twice, culminating in a sword duel. Also the princess is a doppelganger of Romana for an unexplained reason.
A fairly basic plot with low stakes, which could have been improved with tighter writing and directing. Apparently this is a take on The Prisoner of Zenda, which I have not read. Baker and Tamm have a good time. Not what I would call an essential episode by any stretch, but there’s horses and regal garb so there’s that.
Next up: The Power of Kroll