The hindwing spotting of adonis blue males has been discussed before but I couldn't find the post. Anyway, here is one I found today that I think is the most extreme I have seen yet. It was flying not far from where I live in Switzerland, rather than the UK, but the normal range of variation is the same out here as in England.
I won't be offended by no replies! - I just remembered the topic coming up before and thought this was quite a striking illustration of how spotty they can be.
Guy