gery balck cap, long, thin stem of same colour, gills fairly widely spaced
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.
How big was this?
cap abou 1" across and 1" deep. Thin stem about 4 "
In that case I think Panaeolus papilionaceus is probably what you have got.
Lat/Lng: 51.2996, -0.715
OS grid ref: SU896563