Snails
When cleaning out the cupboards in the side of the shed some damp was found in the back of the lower ones. Looking round the side of the shed, I discovered a large pile of items that were leaning part way up the side of the shed. On investigation, I found the totally rotten remains of a scaffolding plank. I found the metal end of the plank and a load of mush, some plastic pipes (white and grey), some hardwood that was mostly rotten, some rusty angle iron, some large plastic trays, other bits of rotten wood and some snails (they liked the pipes). The gap down the side was too narrow to get into so I dragged it all out with a hoe (found elsewhere in the garden) and dropped the level down by about 4 inches.