David, this is, for me, a really interesting observation. I have only really ever seen this species perched. The only time I've ever seen them in flight was when they'd been disturbed, after which they very quickly settled again. Your comment about it not stopping interests me. Can you expand on the behavioural aspects of your observation?
The dragonfly did not settle, but flew up and down the stream more or less following the same course many times, bit like patrolling its tetritory and or looking for something.