Consensus of Michael Jensen and Ahrex Hooks (soft hackle Blue Dun)
Hook Curved nymph / North Country Spider hook, 10-14
Thread Yellow / Primrose Pearsall's Gossamer silk
Materials
Tail Few fibres from a Blue Dun hen saddle
Body Rear third - just the tying thread, front part - mole dub
Hackle Blue Dun hen saddle or neck
How to tie it
Attach the yellow/primrose silk thread to the hook.
Tie in a few blue dun hen hackle fibres as a tail (optional) and bind them down along the shank.
Dub a very sparse body of mole fur on the thread, leaving the rear of the body as bare thread and adding fur as you go forward, so the thread colour shows through the dubbing.
Prepare a blue dun hen hackle feather, tie it in by the tip, remove the fibres you do not need and keep it sparse.
Wind the hackle a turn or two and lock it in place with thread.
Pull all the hackle fibres back and whip finish with as few wraps as possible, since the silk is thick.
Add a touch of varnish.
Other versions
2 more in the app: As tied by Jim Misiura (winged Blue Dun wet fly), As tied by Michael Jensen.