Sieve-winged Snailkiller (Coremacera marginata)
One of the things I focus on when I'm out and about are wooden fences in the sun, which appear to be magnates for many an insect.
Yesterday, on a single wooden fence, I found two flies (of which this gloriously named fly was one) I'd never seen before, and a number of dragonflies, within the space of a few feet and a few minutes.
Find out more about this snail killer here:

''Coremacera marginata'' is a species of fly in the family Sciomyzidae, the marsh flies or snail-killing flies.
Similar species: True Flies
By Philip Booker
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Uploaded Sep 24, 2021. Captured Sep 23, 2021 15:19 in Silver Birches, 35 Rookery Cl, Brighton BN1 6DQ, UK.