The BBC reports that the "Dainty damselfly" (the name of a specific species, not a description of damselflies in general) has made a return to British shores. Apparently they lost in the great floods over 50 years ago, but have now returned to North Kent, probably blown over the channel from increasing populations in Belgium.

I'll be honest, the pictures don't make it look particularly different from other black and blue damselflies that I see around, so you'd probably need to be quite clued up to identify this one. More info on the species here courtesy of the British Dragonfly society.