Banded General Soldier fly (Stratiomys potamida)
This striking yellow and black fly looked to me like a wasp-impersonating hoverfly when I first saw it but it turned out to be neither! It is just a fly despite that bold appearance. It is one of the family called soldier flies because of the smart uniform they wear.
This species was recently given the common name of the Banded General. Its larvae feed on algae and rotting vegetable matter in very damp areas so you will often find the fly itself in similar habitat either on the ground laying eggs or perhaps nectaring on nearby umbellifer flowers such as Hemlock-water Dropwort, Hogweed and Angelica.
One of three similar species so one need a careful eye to distinguish which one, the 'eye' that helped me with this one was the I-Spot website!