You have a Chaser (Libellula) of which there are three resident in the UK.
Four wing nodes, four black spots, hence quadrimaculata.
Don’t be distracted/put-off by individuals of form praenubila which have larger/stronger black markings.
Very broad abdomen. Extensive dark patches on both fore- and hind-wing roots, the latter encompassing the discoidal triangle.
Restricted dark patches; only a hint -more of a thin line – on the fore-wing root and that on the hind-wing root stops short of the discoidal triangle.