Confidence: I'm as sure as I can be.
Notes: 1) that it often occurs in white or near white,eg http://www.galerie-insecte.org/galerie/libelloides_coccajus.html & wikipedia & EOL. The form's identical to the coccajus in Collins wild guide:insects. 2)Has 2 key features (a) that the "webbing/netting" (French=nervures) on the forewings is black, not yellow as in L.longicornis; & (b) the black patches on rear wings extend nearly to the bottom of the rear wings (true in my pic & collins, & all the net pics). These features distinguish them from all the other Libelloides in EOL (42 pics, 9 species). see comment