Small black bug sheltering on a White Dead-nettle. Sorry about the poor photos - not much light.
No interactions present.
Probably Lygaeidae - because some Lygaeidae have thicker front femur.
Miridae, Saldidae and others usually have thicker hind femur or equal.
Looking at dark Lygaeidae about the right shape on the British Bugs website:
Not Megalonotus - last antennae segment too short on my bug
Not Stygnocoris rusticus - antennae OK but end of wing cases gently curved
Stygnocoris fuligineus & S. sabulosus too small
Plinthisus brevipennis - pronotum wrong shape
Possibly Drymus -
Heavy front femur
Antennae segments with second slightly longer
Pronotum with slight transverse grooves in the middle
Probably not brown enough for D. brunneus
The light patch in the apex of the triangle behind the place where the wing cases meet looks like D. ryei
D. sylvaticus often has browner wing cases
However, I think it unlikely these photos are good enough to take it to species level. I'm hopeful of having Drymus confirmed but I haven't been able to compare it with species not yet illustrated by British Bugs.
Lat/Lng: 51.0451, -1.3392
OS grid ref: SU464275
On a White Dead-nettle growing beside bushes bordering a path, chalk.