Confidence: I'm as sure as I can be.
Notes: Shape of exuvia (and adult) points to a Libellulid (= Chaser, Darter or Skimmer)
Dark bases to winhs exclude Skimmers and Darters; this leaves Chaser. No darl spot at nodus so not Four Spotted Chaser; can't see any orange in wings so not Scarce Chaser. This leaves Broad Bodied Chaser as the most likely ID. Ther has clearly been some problem with the emergence: the pterostigmata are already dark so it's been stuck there for some time.