Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
No interactions present.
But it looks like one of the larger Willow-herbs with a gall or similar problem. But I could be entirely wrong (it has occasionally happened!)
Looks like gall-midge Wachtiella persicariae on the leaves of Amphibious Bistort. in which case this observation should in plants or inverts group
Lat/Lng: 54.0, -2.9
OS grid ref: SD4760