Gasometer Bishops Waltham.
4 of us set out one evening to paint an arrow and HA on one of Hamble’s rejoining points.
A few days later with my instructor in the Baron..Pat Courtney (he who left a hurribomber wingtip on a tree stump somewhere out east)..asked why the arrow was pointing the wrong way?
Twas how I learnt that the top rotates with the change in volume in said structure.