Common Yellow Splay Erioptera flavata
I used Stubbs to identify this but unfortunately it doesn't appear to be possible to separate female Common Yellow Splay Erioptera flavata from Thorned Yellow Splay Erioptera meijerei. The latter is much scarcer and mostly found in the Norfolk Broads, but there are records elsewhere including, going from the NBN Atlas, one from the Dereham area so not far from this. As well as being more likely to be flavata on basis of scarcity, the time of year also points more towards flavata as meijerei peaks later on. However, unless someone more experienced tells me it's safe to record it as flavata, I shall leave it as either-or.
female Common Yellow Splay Erioptera flavata or possibly Thorned Yellow Splay Erioptera meijerei showing wing and cerci, Wendling Beck Environment Project (Norfolk, UK), 25th June 2025