Anomoia purmunda, Tephritidae. This is a pretty frequent picture winged fly. The larvae feed in the fruits of Hawthorn and other berries of Rosaceae and Berberidaceae. Consequently, it commonly occurs in gardens with such fruiting trees and bushes. I have also found that it is attracted to drying paint. Presumably something about the solvents that are given off mimics whatever it is that nomally attracts it to ripening fruit!