Actually, on this version of the song, which you can listen to below, Geoff Nicholls plays bass.
“I recently found this SONY C-90 tape cassette amongst the thousands in Geoff Nicholls’ archive. On the inlay card is written ‘ ON & ON HEAVEN & HELL ORIGINAL VERSION GEOFF PLAYING BASS’. Inside the cassette case was a Maxell UD 90. On the A side again in blue ink ballpoint is written ‘LADY EVIL (crossed out) BLUES + SLAPBACK’. The B side is written ‘On + On HEAVEN HELL ORIGINAL GEOFF ON BASS’ nowhere does it say that this is Black Sabbath on the cassette. At the end of the uploaded song you can hear talking that sounds to me like Geoff talking then laughing.
“I have uploaded the most complete version closest to the album version. This recording, in my opinion is from July 1979 in their rented house in Bel Air, California. On And On Heaven And Hell may have been the original working title.”