Dark-winged Chrysogaster Chrysogaster solstitialis

I initially had some difficulty keying this using Ball & Morris's "Britain's Hoverflies" as the out cross-vein semmed to be as recurrent as shown there for Neoascia and Sphegina (the Stubbs & Falks "British Hoverlflies" didn't have this problem, the only place where the recurrent cross-vein featured in the key it explicitly excluded the Neoascia-type almost right-angled entry). Also the metallic blue reflections on the centre of the tergites suggested I should interpret these as metallic, although eventually when I removed the wings for a clearer look I realised that despite the metallic blue reflections here, the surface was clearly dull and contrastingly different from the shiny metallic black edges to the tergites (importantly except tergite 1 which was dull to the edge).

female Dark-winged Chrysogaster Chrysogaster solstitialis showing wing and upper surface of abdomen, Ling Plantation, North Elmham (Norfolk, UK), 4th June 2022