What's this called?

Visited Newby Hall today - glorious weather, beautiful gardens, interesting sculpture trail and lots of these flitting about. How lovely. But what are they called? Damsel fly, dragon fly? New to me, love the deep blue body and the spots on the wings.
Bet one of you macro blippers will know.

Updated: couldn't wait - looked on the web - it's a damselfly - a male Banded Demoiselle
here's a vid showing them in action