Emperor Dragonfly (female) - Anox imperator
An impressive Dragonfly, and it should be, given it's the UK's largest.
It's also an impressively fast flyer and can often be seen patrolling or hunting close by water. Although it will travel further if necessary.
This is a female laying eggs, as one is in the accompanying video:
The emperor dragonfly or blue emperor is a large species of hawker dragonfly of the family Aeshnidae, averaging 78 millimetres in length.