Length 4 to 5 mm.  This genus has a distinctively-shaped pronotum and the front femur has one large tooth and several small ones. Drymus sylvaticus has reddish-brown forewing and entirely black scutellum and pronotum. The legs lack long hairs.  There are two rectangular dark marks forming a V-shape on the forewings, by the tip of the clavus.  

Other Drymus. 

Detailed examination of the specimen is needed to identify the species.

Amongst moss, grass and leaf-litter on dryish soils.

Adults can be seen all year round.

Common (ref.: British Heteroptera checklist 2021 on British Bugs website) 

Frequently recorded

https://www.britishbugs.org.uk/heteroptera/Lygaeidae/Drymus_sylvaticus.html