I have no idea... but I like the photograph!
Thank you, Ed!
Mike, the site you suggested only handles insects in North America and this was taken in England, in July a few years ago. I found a site in England called Ask A Biologist and posted a link to the shot there: their comments are here
: they didn't find it easy to identify either. Sadly, I can't find a way to post a follow-up there so I can't tell them the date. I did send an email to the dragonfly society, but they've not replied as yet.
So, there we are. Pierre, I suspect Aeshna affinis is most likely. Next time I see one, I'll make sure I get its anus in shot .