Regular correspondent Bob emailed a picture of a Damselfy he was having trouble identifying. The difficulty with Damselflies is that usually the male, female and immature examples are very different and are sometimes available in multiple colour forms beyond that. But also some species are remarkably similar and hard to pick apart.
However after a bit of a hunt I'm pretty sure it is either a female Azure damselfly or female Common blue damselfly (though the pictures on that last link don't show it, due to aforementioned variations).
Apparently the female Azure damselfly "can be distinguished from females of the Common blue damselfly by the absence of a spine below the 8th abdominal segment". Unfortunately the photo doesn't lend itself to making that judgement and I'm not entirely sure what to look for anyway, being unfamiliar with such spines. It can get pretty technical and into the really fine detail apparently! Are there any insect experts out there who can help?
Update: Thanks to S Barton who posted a comment with this great BBC page which has a couple of very clearly described and illustrated tips to tell Azure from Common blue. And with its help, our picture above is clearly an Azure.