A best guess from my cheap ' n' cheerful insect guide: looking for a correction or confirmation.
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I'd agree that this is Tachina fera - would you like to add that as the identification (click on "add a revision") so we can agree with you?
The most similar species is Nowickia ferox - if you look at the second of the three antennal segments, and the tibiae of the legs, they are orange in T. fera but dark brown/black in N. ferox.
Entomologist and biological recorder
I'll agree with Tachina fera - it's a nice clear photo and there are only a very few other UK species that look similar - for this species ID we can see all the bits we need to see. I'll add the record to the Tachinid Recording Scheme dataset later on today.
Tachinid Recording Scheme
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Lat/Lng: 54.6, -1.4
OS grid ref: NZ4028