Common Hawker (Aeshna juncea)
Hawkers derive this collective name from the way the species in the family fly around their territory almost continuously, just occasionally resting. They defend their territory fearlessly and will even approach human beings who enter their patch to check them out! Whilst that can be a bit disconcerting the dragonfly is, of course, totally harmless to people. This 'hawking' seems to form two purposes, the same to driving forces behind all of nature; one is food and the other reproduction.They are hunting for food and hunting for a mate!
The tricky bit with hawkers is telling the species apart because of this constant movement but we ttend to have three here in Dorset, the most common is the Southern Hawker, and the rarest is the Migrant Hawker. The third species is the Common Hawker and, peversely, is not the most common.
If the insect looks green and/or blue then it is probably the Southern Hawker and most will be. If it is brown and blue it is the Common Hawker and if it looks brown/black then it is probably Migrant Hawker but you really do need to see them at rest like this to be certain.