Seeing Double

I've been chasing butterflies about today without a single one sitting still for the camera. Then I saw this modest white Cabbage butterfly sitting still on a leaf. Even when I approached for a close up it wasn't spooked.

Then, I realised why. This isn't one butterfly but two and I'd burst in on them mating. They obviously had an, 'I've started, so I'll finish' attitude as they let me blip them. One or two other males flitted around them but they were too late - this lady was already taken.