You have a male of one of two Lestes species, Emerald Damselfly/Common Spreadwing (Lestes sponsa) or Scarce Emerald Damselfly/Robust Spreadwing (Lestes dryas).
Males of these species are complicated by the fact that both develop pruinosity when mature and this masks some of the distinguishing features. The pruinosity itself can vary in extent and can help distinguish them but is not always clear/reliable as this diagram explains.
The reliable way of telling the males of these two apart is the shape of the lower appendages, which does require a good, clear photograph at a suitable angle. Appendages don’t lie.
Emerald Damselfly/Common Spreadwing (Lestes sponsa) male appendages
Scarce Emerald Damselfly/Robust Spreadwing (Lestes dryas) male appendages