A gang of these came around our pond for a few minutes, buzzed around furiously and noisily, occasionally briefly settling on water lily leaves. Then they disappeared. Nothing like the usual hoverflies that hang around flowers for ages.
This beauty is a marsh hoverfly. Magnificent body markings and lace wings! Judging by the Wikepedia entry this appears to be a female.
The only way to photograph this was using the full telephoto capability of my Panasonic ZX200. She was maybe dancing, or about to take off, in this pic.
I first managed to identify this hoverfly on the UK safari website.