About 5 yards from high tide mark. Found in a salt water meadow. (Meadow which is frequently submerged in sea water).
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.
A web site in the Neatherlands/Germany? lists 3cap fungi an Agaricus bern....? salt tolerant, Marasmiellus sp , & Meadow Blewit; yours is definitely not the latter.
It appears to be more like an Agaricus sp, its shape is similar to it. But The Marasmiellus sp seem to be much different looking to this one. I will keep an eye on its development and see if it shows any identifying features
Lat/Lng: 55.0439, -5.9639
OS grid ref: NW468793