Holly blue

I have rarely seen a blue butterfly in my garden and I don't think I have ever seen a holly blue here before.  I have several holly trees but this one was feeding on borage in the kitchen garden.  Its technique was to land on the top of the flower and then walk over the side to feed upside down.

As far as I know the only two blue butterflies this far north are the common blue and the holly blue.  Given that both species tend to sit with their wings closed they are easy to tell apart.  The underside of the holly blue is silvery blue with black spots whereas the common blue is grey(♂) or buff(♀) with orange, black and white markings.

Holly blues sit with their wings closed and open them only occasionally in weak sunshine.  I talked nicely to this one and it did so, just for a moment.  The upper wing had grey/black borders showing it is a female (the male is all blue).