Spring Fieldcap - Agrocybe praecox

Convex light-brown/ochre cap, becoming flatter as it ages, with a darker centre.  Surface of cap cracking in dry weather.  Gills adnate, pale brown, darkening with age; spore print brown.  A thin, pendent and short-lived ring on the stem.  The stem base usually has white hyphal cords.   

other Agrocybe - and small brown mushrooms

Photograph top down, in side view and underneath cap to show gills and full length of stipe, including stem base; note habitat and substrate.

Woodland, scrub, grassland, roadside verges, gardens, often on woodchip mulch

spring and early summer

This is probably a species complex involving several other Agrocybe, not yet determined as British species.