Unidentified agaricus

Unidentified agaricus

Observation - Unidentified agaricus. Description: Found beside garden path under mixed hedge of mainly hazel and holly. Two mature specimens only. Diameter of cap 13cm and length of stipe 11cm. Mature cap almost flat but slightly convex. White with inky brown scales, darkening to an almost black spot 2

Found beside garden path under mixed hedge of mainly hazel and holly. Two mature specimens only.
Diameter of cap 13cm and length of stipe 11cm.
Mature cap almost flat but slightly convex. White with inky brown scales, darkening to an almost black spot 2-3cm across at the centre. Flesh white. Gills crowded and free, pinkish grey. Stipe white, cylindrical and slightly bulbous at the base. No more than 2cm in diameter. White, membranous ring, descendant. Stipe is slightly fibrous and faintly hollow inside. I've been through my fungi guide, paying special attention to the agaricus ones but can't settle on any one.
The cap is too dark scaled to be silvicola,