Confidence: I'm as sure as I can be.
Notes: Identified by JOHN CHAINEY: Despite the thoracic spot, I'm inclined to think that it's an unusually well marked abbreviata. The rather elongate and not very prominent discal spot, brown patch just beklow the discal spot, wing shape and date fit with that species. E. virgaureata has a more prominent, less elongate discal spot and is generally a more greyish looking species. Although the white thoracic spot seems uunusual, I do have a couple of well marked abbreviata that have a pale spot (albeit not quite as bright as in the photo).