I believe this is the female of the same species as the male in the previous post, the Migrant Hawker... This one landed on the top of a wisteria twig, high above the garden... embiggen for context.
I can completely see why the period of decorative art I love most adopted dragonflies as a motif - Lalique did it here in jewellery, in a piece which was the centrepiece of the V&A's exhibition a few years ago... Gallé did it here in furniture but I've also seen him use it in marquetry and glass design... and of course Tiffany did it in glass - this is a repro lamp but I have seen an original, probably in the same V&A exhibition... What I love about art nouveau is the combination of engineering and fluidity, hard substances and soft shapes, strength and elegance; looking at a dragonfly is like observing art on the wing.
Some interesting stuff about dragonflies and culture at Wikipedia's page. (While I'm your typical sniffy librarian on taking Wikipedia as your one and only source for academic research, I use it all the time for general interest...)