Longitarsus luridus
This keyed to luridus using Duff but needed the genitalia examining to make sure. It was about 1.9mm long.
male Longitarsus luridus showing hind leg, base of antenna and aedeagus (3 views), North Elmham (Norfolk, UK), 21st March 2023
I identified this one as luridus at the time. Subsequently I was struggling over another beetle which reminded me of this one and which I eventually identified as Longitarsus parvulus. One of the options I had struggled to rule out was luridus and the experience made me think I should re-examine what was then my only record of luridus. Unfortunately I hadn't kept the specimen and don't appear to have examined its genitalia - I don't think I can confirm it from these two photos and in view of the lack of evidence I don't regard this as a definite record. My notes say that it was dark reddish-brown, not as black as it seems in the photos.
Longitarsus sp., identified at the time as Longitarsus luridus, North Elmham Cathedral Meadows (Norfolk, UK), 27th September 2019