A female Calliphora vomitoria (Diptera: Calliphoridae). The yellow ruff around the neck is a characteristic of this species.
This is a male:
Photos taken in Whiteknights Park, Reading, UK, on 2012-08-14 (female) and the field below Chazey Wood, near Caversham, UK, on 2012-09-01 (male).
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