Small fly with patterned outstretched wings.
No interactions present.
The wing looks a very good match for Rhagoletis meigenii. See http://www.diptera.info/photogallery.php?photo_id=2867. It seems to be a very scarce species in UK, though, and I am not going to be rash enough as to propose an ID. Maybe someone else will be braver.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
See also comments at
Lat/Lng: 52.061168, 1.159024
OS grid ref: TM166450