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I have to disturb Dr. Ackland for ID...

I found that there is no need to disturb Dr. Ackland, because in Dr. Ackland key for British Anthomyiidae, there is key for Fucellia species.
Gena narrow, no hairs at all between presutural ac, male f3 basal ventral tubercule rounded at end.
Fucellia tergina.