Ophion ventricosus

I used Gavin Broad's key to nocturnal Ichneumonidae to identify this. It keyed fairly straightforwardly - the only slight hesitation I had was in the couplet getting it to Ophion - the mandibles were broader at the base than the tips but twice as broad? Probably not. It had a glabrous area within the discosubmarginal cell but it wasn't particularly large and didn't extend over vein Rs+2r which was gently curved not sinuate (maybe just ever so slightly but barely perceptibly so and certainly not as much as shown in the figure for Enicospilus. Just in case, I did try keying it as Enicospilus and reached Enicospilus inflexus. Although nothing in the key clearly ruled that out (I wasn't sure about the antennal socket being almost contiguous with inner margin of eye - not at the side but maybe more at the front?), photos of this species online look nothing like my wasp. So I'm confident I went the right way at that couplet which led to Ophion, and the species key for Ophion led pretty simply to ventricosus.

Note that the photo of the forewing and hindwing below was taken in such a way that the photo has lost any hint of the yellow in the membrane - in reality this was quite strong as shown in most of the other photos.

Ophion ventricosus showing right wings, close-up of discosubmarginal cell, mandibles and bdoy from side, Wendling Beck Environment Project (Norfolk, UK), 14th May 2023