The Sontaran Experiment as the name suggests, is a bit of an experimental story, just not in the way you might expect.
Would you believe the Tour if we told you it was actually a four part story instead of a two-parter (sort of the inverse of Hartnell’s The Ark which disguised two two-part stories strung together into a four part story)? It’s not of course unless you consider a special quality it uniquely has over any other story in the canon.
Tom Baker injured himself rather badly breaking his collarbone whilst on the rocks of the Dartmoor location where the OB shooting took place. Without knowing this one could watch The Sontaran Experiment and see a bit of stunt-doubling where needed but nothing more. Knowing this however becomes a game of watching Baker carefully, seeing which scenes occurred before his accident and which after, given how he rigidly kept his left arm concealed and immobile, or by the necessarily unconvincing doubling during the fight scenes with the Sontaran towards the end of the story.
That’s the game, but not the only reason to watch The Sontaran Experiment.
A two-part story was a real rarity in Doctor Who, with this being the only example between The Rescue 11 years previous and Black Orchid 7 years hence. And given this was the classic series, the inherent structural differences make these stories quite different from a single episode in nu-Who. Not better, just different.
Images and new HD-caps for The Sontaran Experiment are online.