This is the common hawker (Aeshna juncea). The two photos above show a male in flight - easy to see but not so easy to photograph. Below is are two males at rest, something they probably do a lot but usually out of (my) view. This afternoon I was lucky.
This is a female at rest. Both sexes have a distinctive yellow costa, the leading edge of the wings.
Here is a female ovipositing at the edge of the pond.
After mating the female lays her eggs alone but runs the risk of being accosted by another amorous male, as happened to this one.