Many years ago (1970?)my physics teacher at school was Frank Addis, he and I were members of the North Manchester Caving Club. We did Alum on ladders and I was told at the time that the tub was used to give tourists trips over the top of the shaft. Apparently on one trip somebody fell out and it was decided that it was probably not a good idea to continue doing it. I believed it at the time and hadn’t really thought about it since. With hindsight I probably deserve the most gullible caver of the year award, but it did make a good story.