“The Return”, Inside the Castle

On these albums

Doctor Who: The ArkPaul Erickson and Lesley Scott starring William Hartnell, Jackie Lane & Peter Purves · 2006Soundtrack

Doctor Who: The TV Episodes - Collection SixVarious Artists · 2013

Source: MusicBrainz recording cf344bbc-a1e3-4aa6-8408-271d5f3d8fbb (CC0).