Yellowing Knight - Tricholoma scalpturatum

The cap is conical initially, flattening to a convex shape. The colour is pale to dark grey, wth darker pointed scales in concentric patterns.  The  white or pale grey gills become yellow as it ages and rots, or when bruised.  The stem is pale grey, sometimes with the remains of a white veil near the top.  The smell is rancid-mealy

There are several similar grey Tricholoma, but the yellow staining on old and bruised speciens of T scalpaturum is a useful identification character

yellow staining

Photograph from top down, in side view and from underneath to show gills and full length of stipe.  Note habitat and substrate.  Your photos must show the yellow staining on bruised or old specimens.  Microscopic examination of a specimen by an expert may be needed.

Deciduous trees, typcally oak, lime and beech.

Autumn.

Widespread and common (Kibby, Vol, 2, 2020)

Occasional in Leicestershire and Rutland.

https://www.first-nature.com/fungi/tricholoma-scalpturatum.php