About 3cm long. At first sight I thought it was a large earwig, but it is much too big and doesn't have the distinctive forceps
No interactions present.
I just had a look in Harde, Hammon, Severa on Beetles, and while this is certainly in Staphylinidae, none of the ones illustrated there seem big enough. Maybe 3cm is an over estimate, but it was at least 2cm...
... or maybe just a genus ;-)
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
The pictures on the BioImages site confirm the identification.
Lat/Lng: 51.08418, 0.02536
OS grid ref: TQ419336
In Ashdown Forest, on a sandy bank in woodland (birch, beech)