The Scarce Chaser is very similar to the much more common Black-tailed Skimmer which can normally be seen all around the lake. This Scarce Chaser is the first one I have seen at Croome (living up to its name) and was spotted next to the Chinese Bridge. They are only mostly around in June but can sometimes be seen in May and July.

The differences between Black-tailed skimmers and Scarce Chasers are the width of the abdomen (tail) - skimmers are slimmer, and the chasers have a black thorax (shoulders). However, the main (and most obvious) difference is that the skimmers have dark green eyes, and this Scarce Chaser has vivid pale blue eyes as you can see in the photo below...