All black beetle. Short wing case. Sparse hairs on pronotum and abdomen. 19mm.
No interactions present.
Could this be Tasgius ater? Proportion and shape look right. Only one site I found mentioned size - c23mm, larger than my specimen.
The instar confusion; happens in the larval stage, if my sources are correct.
So much to learn!
Lat/Lng: 51.224166, 1.193705
OS grid ref: TR230520