No interactions present.
This fly has black on its hind tibia making it R campestris - R. rostrata has tibiae that are entirely orange (Stubbs & Falk)
This may be a very orange specimen of campestris, because of the dark lateral margin to tergite 3. However, the tibiae look orange to me, including the hind tibiae, where the usual dark ring of campestris is not there. The hind metatarsus is dark, but looking at picture 2, I don't think the tibia is especially. In addition, the snout does not look very long in picture 2 and the scutellum is very pale...both features of rostrata.
rostrata does not occur where I am (apparently), so I don't have first-hand experience of it, though. I would be interested to know what an expert thinks.
My Flickr photos...
It looks as though I may have confused where the tibia ends and the tarsi begin.
This fly was in somewhat shaded conditions. I went with the black markings criterion rather than orange colour because, as I originally had the camera set up, images of fly abdomens tended to be somewhat biased to orange at low light intensities. I am still exploring this.
Lat/Lng: 51.4337, -2.7624
OS grid ref: ST470707