Lead Belle Scotopteryx mucronata
This species is very similar to July Belle and really needs dissecting to be 100% sure. Although formerly believed to occur in Norfolk, all specimens that were checked proved to be July Belle, so it is no longer believed to occur here.
The species has been lost from much of its UK range, and I think is now only widespread in SW England and Wales. I was therefore expecting this individual found in Cumbria to be a July Belle, but it turns out it was a Lead Belle. It seems there is a small population continuing in the SW Lakes at least.
female Lead Belle Scotopteryx mucronata showing genitalia, Irton Fell (Cumbria, UK), 12th June 2021