Bee fly on a flower.
No interactions present.
How are you ruling out other species? Without a view of the wings, it is difficult to be certain it is major, even if it is quite likely.
My Flickr photos...
Thanks for the comment and I do take on board the point. I did see the wings at the time (I was watching a couple of them for quite a while yesterday) although this information was not available in the photo. I then double checked the ID on the Natural History Museum site.
iSpot is (although photography based) a wildlife ID site not a photograph ID site so if you provide a description of features observed (but not photographed) in the notes section it would be possible to agree with your ID (if the description is thorough enough) even if the photo does not show it.
In this case if you can add your description of the wing features to this discussion that is probably enough to allow agreement with the species level ID.
Lat/Lng: 51.6, -0.8
OS grid ref: SU8595