I photographed this butterfly last year in central Spain. It seems to me that the hind wing has the characteristic scalloping of a Powdered Brimstone (Gonepteryx farinosa) but that would put it well outside the published range.
The butterfly does have a large chunk of the hind wing missing next to the scalloping but the scalloped edge seems to be intact. So is this an abberation or an out of range specimen?
I see what you mean about the hind wing scalloping Alan and on that character alone it arguably fits for farinosa. However, the costa looks too straight to me so I would lean towards rhamni. I will check with our lepidopterists though and report back.