This appears to be a variety of Horse Fly
No interactions present.
Looks like Empis opaca having red thighs.
Is there a good key to Empis, as this looks like E. tessellata to me, but I would like to be able to key them out properly.
My Flickr photos...
Lat/Lng: 52.529556, 0.063288
OS grid ref: TL400944
Gault Wood (Woodland Trust)