less than an inch in length, feeding on plants next to a small lake. Possibly part of a group as many other similar / identical specimens around
No interactions present.
It is either S. torvus or S. vitripennis (female, with black base to the hind femur). To separate these we would need a lot more detail.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
I would not discount S.ribesii, either, as the hind femur is barely visible and any black looks very limited. It is a Syrphus, anyway.
In August, there are always a lot of Syrphus around, but this year there was a large immigration from the continent, too, so there were very large numbers at that time.
My Flickr photos...
Lat/Lng: 52.5026, -2.9423
OS grid ref: SO361898
on parkland next to a small lake