“Horse of Destruction”, Scene 4: Cells, Troy

On these albums

Doctor Who: The Myth MakersDonald Cotton starring William Hartnell, Maureen O’Brien & Peter Purves · 2001Soundtrack

Doctor Who: Adventures in HistoryWilliam Hartnell, Patrick Troughton with linking narration by Peter Purves & Frazer Hines · 2003Soundtrack

Doctor Who: The Lost TV Episodes - Collection OneVarious Artists · 2010

Source: MusicBrainz recording aff0bb7c-f010-4b0b-add3-8829e38eafc3 (CC0).