These are recorded inside the Inchindown Oil Tanks, which hold the world record for longest reverberation time.
From this video: www.youtube.com/watch?v=lLUcOFwZvyY
This was recorded by me. You can use it if you credit me as "Matt Gray mattg.co.uk" beside your work.
Røde NTG-2 shotgun mic: amzn.to/2zqA9Ki
Røde NT-4 stereo mic: amzn.to/2DVxJHg
Roland R44 recorder: amzn.to/2PRVRRG
Thanks to Tom Scott, Preston, Alan, Allan, and the Bannerman Group.